Some of you may remember an old thread I started talking about modifing the 60° intake on the 2.8 in the Fiero. The original testing didn't come to pass as I'd hoped due to numerous difficulties, but I've found another test mule so we can see what happens. Alex4mula responded on the forum that he might be interested in doing some testing and after swapping some emails we came to an agreement, so we've been running some tests.
First off, the original thread is at PFF HERE so you can go back and get up to speed again or if you weren't around or missed it in the first place.
To make a quick summary, many of you have bored TB's and intake and my opinion then (and now) is that due to the restrictions in the neck (snorkel) they are of limited if any value. This picture shows the restriction in the snorkel well back from anything that can be bored out.
You can see that boring the TB and first part of the neck is going to be of limited usefulness. Since I was going to get rid of that restriction, I also did some calculations on trying to move the powerband up a bit and increasing the plenum volume. You have to be careful when playing with this because if you move the powerband up too much you get out of the range of the cam and the rest of the engine and actually costs you power and torque. You also have to be careful about increasing the plenum volume too much or throttle response begins to suffer.
By crunching some numbers, a 500 rpm shift in the powerband should require removing about 60 mm of the runners. This turned out to be hard to do and have things stay relatively simple, but I did get about 52mm taken off them by milling the top out and cutting the runners back on my mill. The manifold looked like this before we started rebuilding.
I took a guess at increasing the plenum volume and decided to stay at about 2 times the stock volume. Even with a sloped top, it ended up a little more than that and I was very concerned about throttle response with a volume of about 2.3 times the original. Here's a couple of pictures of what the intake looks like after the modifications
The modifications took longer than I thought primarily because I wanted it to be as simple to change over as it could possibly be. There is no provision for EGR with this manifold at all but the location for the PCV had to moved a bit and that took a bit of modification on Alex's part. Many things have to be addressed like throttle cable position and attachment, location of all the vacuum fittings, overall height (we're at the absolute limit here now with the stock decklid on Alex's car), and numerous other little details. Here's a picture of the manifold on his car.
I warned Alex that it wasn't pretty, it was an R&D piece. We had problems welding parts of it due to contaminated rod, but everything is tight and he has a normal idle so there are no leaks. I did shoot a quick coat of paint on it and stuck a little Fiero decal on it to pretty it up a little.
I suppose you're wondering what the dyno showed? Well, I'm not going to tell you At least not in this post. But it will be in a post right after this.
John Stricker
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01:39 PM
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Howard_Sacks Member
Posts: 1871 From: Cherry Hill, NJ Registered: Apr 2001
Hey WTF! I was hoping for a little resolution at the bottom of this thread and instead I find nothing but more waiting. I'll post the first guess in anticipation of you posting the results after some people guess.
Stock 135 HP
with modified plenum I guess at about 145 HP
With a slight loss of low end power and barely noticeable loss of throttle response.
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02:51 PM
Alex4mula Member
Posts: 7403 From: Canton, MI US Registered: Dec 1999
I'm guessing that the maximum power is up a bit. Not much. I'm also going to guess that it's running leaner at the top end than it did before. Perhaps, too lean. (You did have a chip programmed for your previous config... right?)
[EDIT] I'm guessing a 5-8 HP gain. ------------------ Raydar 88 3.4 coupe. Coming soon... 88 Formula, presently under the knife.
[This message has been edited by Raydar (edited 02-28-2004).]
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03:01 PM
jstricker Member
Posts: 12956 From: Russell, KS USA Registered: Apr 2002
It will be resolved by, oh, say 4:00 pm today? So guess early and guess often. We won't make you wait for a week or a few days, we've waited long enough already.
We really should make it a little more fair, though. Alex already had a bored TB and plenum, it wasn't a stock upper. He also has a Wester's chip. Alex can maybe chime in with any other modifications that have been made to the engine BEFORE the upper intake change.
I'm not saying that either of these are good or bad things, but it's something you should consider when you make your guess for HP increases.
John Stricker
quote
Originally posted by Alex4mula:
I suggest to try to guess only the HP difference. Don't worry about max HP numbers. So yours would be +10HP.
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03:02 PM
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Raydar Member
Posts: 40712 From: Carrollton GA. Out in the... country. Registered: Oct 1999
Alex already had a bored TB and plenum, it wasn't a stock upper. He also has a Wester's chip.
Since he has the Wester's chip, I'm guessing it leaned out, at least a little. This was based upon a previous post that he made, that said it was "pig rich" on the top end. IIRC, that was before the chip.
[This message has been edited by Raydar (edited 02-28-2004).]
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03:06 PM
Russ544 Member
Posts: 2136 From: S.W. Oregon Registered: Jun 2003
Wow. I just got myself caught up by reading that entire 3 page original thread........ I have a headache now
My adnmiration to John for actually building and trying his ideas instead of just talking about them, as so many others do. This particular project wouldn't be my cup of tea, but I certainly admire the thought and work involved.
Cheers, Russ Camp
------------------ 86 SE350 x 4 speed (my way) 86 SE2.8 x 4 speed (all-option restored) 88 coupe x 5 speed (future IMSA 4.3L project)
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03:15 PM
Alex4mula Member
Posts: 7403 From: Canton, MI US Registered: Dec 1999
Ok. This is an Ed Parks 3.4 (original 3.4 cam) on a 5 speed Formula with these mods (before intake): - Conical K&N with 3" Pipe to TBS - Bored TBS (Darrel) - Bored inlet of plenum (Darrel) - Gasket matched ported runners for plenum, middle & lower intakes - Under drive pulley - Jacobs ignition computer - Jacobs wires - Accel coil - FOCOA headers - Borla exhaust - No catalitic - NGK plugs - 3.3 injectors - TBS Coolant lines eliminated - No EGR - 160° Thermostat - FPR set at 42psi (bumped to 46psi with this new plenum) - Wester's garage kind of lean chip (* more on this below) - Lot's of underhood decals
I got a 2nd chip from Wester but it didn't ran as well and the idle wasn't right. I never dynoed that one nor I asked for a 3rd chip so I changed back to the original. So the current chip is a little lean. Not a big deal because I'll need a reburn once I change the cam.
[This message has been edited by Alex4mula (edited 02-28-2004).]
Now be fair. If you want an accurate guess you're going to have to tell them what kind and how many. For instance an Eibach or Koni or KYB decal isn't going to add any power, but if you have three or four NOS decals.................that's a whole new level of power!
John Stricker
quote
Originally posted by Alex4mula:
- Lot's of underhood decals
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04:40 PM
jstricker Member
Posts: 12956 From: Russell, KS USA Registered: Apr 2002
It's close enough to 4:00 pm (here) and I have errands to run.
First of all, the objectives to this were two fold. One, try to shift the powerband up by about 500 rpm without a loss of torque (and hopefully a gain) so that we can make some extra power and two, get rid of the restriction in the snorkel to see if that's a bottleneck and if we're moving more air through the system. All of this, hopefully, without causing drivability issues or making things worse.
Keep in mind that when you're experimenting with something like this that there's always the possibiity that you go the wrong direction and actually DO make things worse. Alex and I discussed this at length and I was comfortable that he understood and accepted that possibility and that we were definitely in the R&D mode and on the same page.
Ideally, I'd have liked someone to test it with a pure stock manifold, run it on the dyno, take theirs off and then run this one. In the real world, we don't often get exactly what we want. Alex offered to test it for me and had a very recent dyno run on his car to compare it to and he hadn't made any changes since then. He did already have a bored TB and plenum on the car, though, so we don't know how much that makes it differ from a stock manifold. Alex also runs a Wester's chip in his ECM which I think can be tuned to help the results a little bit. Even though his car wasn't a stock 2.8 plenum, Alex was very gracious in taking the time and $$ and running it on the dyno.
So, without further delaying, here's a copy of Alex's dyno sheet.
I posted this graph first because it showed three runs. The first, oldest, is basically stock. The second, back in September, had some changs like the bored TB and the Wester's chip. The last run, yesterday, was only the upper manifold change. First off, we did shift our powrband up by about 500 rpm and it stayed stronger from 4400 rpm through 5300 rpm. I'm not going into how it feels "seat of the pants", but Alex said before he dyon'd it that it definitely felt stronger on top, but was still running out of air.
Second, our HP gains were modest, at best. 2.5 hp. If the TB was worth 3 hp or so, we're looking at a gain of around 5-6 hp for the manifold over stock. That's not very much, but it is around a 5% hp gain over stock and that's not that bad either. Some may argue there was no gain in HP that it was just the day, but I disagree with that because although the total numbers are only a little different, where the power is at has changed significantly.
Third, notice how the A/F ratio has definitely gotten leaner. We ARE getting more air into the cylinders, enough that we're starting to have fuel delivery problems with the current injectors, even with a Wester's chip. IIRC, this was also AFTER Alex had already upped the fuel pressure by a few pounds before the run in anticipation of there being more air available. I'd really like to see what it would do with bigger injectors and another chip. I'd think that another couple or three hp might be available there.
Here's one more chart that shows just the last two runs with HP and Torque
This one really shows the powerband shift more clearly. It also shows that although there was a very slight reduction in maximum torque, once you got up to the range where most performance drivers run there was no reduction and, in fact, a torque increase.
Alex is going to chime in this thread and he can tell you how it feels driving with the manifold and also any other things he wants to throw in that I misunderstood or got wrong.
Was it worth it? That's up to the individual. I think that this manifold, on a 3.4 with bigger injectors and a proper chip, would be worth, AT MOST, 8-10 hp over a stock, Fiero, 2.8 upper intake. It was worth it to me because I wanted to play. If you had someone try to do the same thing for you, probably not. I'm disappointed that it didn't make more power, but happy that it moved the powerband up roughly where I thought it would. I'm also happy that it's still quite drivable and it didn't LOSE any significant torque, as that was a possibility too.
Most certainly, the upper alone from someplace like WCF is not going to flow anymore air than this one did through the bottom manifold. It's my opinion that this is the best you're going to do if you want to stay with the stock mid and lower intake. If I were doing it again, I'd suggest the Edelbrock 60° 4 bbl lower with either a carb or a Holley 670 Pro-Jection if you wanted to go FI.
John Stricker
PS: not a bad way to make my 2,600th post.
[This message has been edited by jstricker (edited 02-28-2004).]
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04:54 PM
Alex4mula Member
Posts: 7403 From: Canton, MI US Registered: Dec 1999
Great detailed post John! I have to add couple of details and one correction. First, the dyno run # 2 was not stock. It was the same setup with all the mods I mentioned above but I was using a 2.8 Hypertech stage 3 "off-road" chip. Off-road because it is supposed to be used without cat and a 160° stat plus it eliminates the EGR. On dyno run # 5 I just added the new Westers chip. Dyno run# 9 I just exchanged plenums. As you can see all numbers are SAE corrected for a fair comparison. No weather bs here. Now, I have to disagree with the need of new injectors. These should flow well enough for this and more. It just needs to be added to the fuel curve on the chip. Before with those injectors and Hypertech chip the car was running very rich. I told that to Westers and I guess they took of too much fuel. So is a mater of putting it back again. Overall the car drives fine and I didn't notice any drivability issues with the new intake. But to be honest I was expecting a little more HP change. There is a huge difference between the stock intake inlet pipe and this one. John has some pics of this that he may want to post (PIP doesn't work for me ). So I thought maybe that was a big restriction. But like we said, this comparison is between a Darrel's bored TBS/plenum and a bigger plenum and not a totally stock plenum on a 3.4. So I think you can expect at least 5-8HP with this change on a 3.4. My next step is to add the H272 cam and a set or roller tip rockers I have lying around from the previous engine. If I have time I may try to mod a little more the middle/lower intakes. After that back to the dyno again. My goal is to try to get to 160+rwhp and then add a turbo
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05:31 PM
Raydar Member
Posts: 40712 From: Carrollton GA. Out in the... country. Registered: Oct 1999
Good tests, guys! John, Sounds like you were pretty much on the money with your calculations, regarding where the torque curve would end up. (500 RPM higher?)
For some reason, I thought you might go to a larger TB and "neck", similar to the WCF intake. That, coupled with your larger plenum - shorter runner design would be interesting. (From the school of "If 'more' is enough, then 'too much' is just right.")
You gonna start producing these? Looks like the gains are equivalent to a set of Sprints.
------------------ Raydar 88 3.4 coupe. Coming soon... 88 Formula, presently under the knife.
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07:01 PM
jstricker Member
Posts: 12956 From: Russell, KS USA Registered: Apr 2002
I don't see a reason to produce them, personally. As an experiment to see what's going on, it was fun. To make HP quick and as cheap, buy some real parts.
I'm fairly certain in my mind that a bigger TB and snorkel at this point is not going to help at all. To me, it seems that we have gotten to the point that it's letting all the air in the mid and lower can pass. You really can't believe how open this system is now. There's just nothing in the way and we picked up, at most, 10 hp over a bone stock system. To me that says that there's no point in beating a dead horse any longer and other than minor tweaking of the power band, to really go further requires more drastic steps.
I'm glad people found it interesting. Sometimes I get sidetracked on my little projects and *I* find them interesting, but nobody else does.
John Stricker
quote
Originally posted by Raydar:
Bravo!
Good tests, guys! John, Sounds like you were pretty much on the money with your calculations, regarding where the torque curve would end up. (500 RPM higher?)
For some reason, I thought you might go to a larger TB and "neck", similar to the WCF intake. That, coupled with your larger plenum - shorter runner design would be interesting. (From the school of "If 'more' is enough, then 'too much' is just right.")
You gonna start producing these? Looks like the gains are equivalent to a set of Sprints.
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07:11 PM
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Scott-Wa Member
Posts: 5392 From: Tacoma, WA, USA Registered: Mar 2002
I for one liked this post, it was an interesting experiment.
If the test vehicle is really running over 17:1 A/F ratio, there is a lot more power to be had, that is aweful freaking lean for under load. It should be running about 12:1 or so for peak power WOT. Stochiometric is 14.7:1 which is where most computers are trying to hold the system unloaded or under light load for best emissions/mileage (vehicles of this vintage... this doesn't apply to a lot of stuff being built today).
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07:33 PM
Russ544 Member
Posts: 2136 From: S.W. Oregon Registered: Jun 2003
I'm fairly certain in my mind that a bigger TB and snorkel at this point is not going to help at all. To me, it seems that we have gotten to the point that it's letting all the air in the mid and lower can pass. You really can't believe how open this system is now. There's just nothing in the way and we picked up, at most, 10 hp over a bone stock system. To me that says that there's no point in beating a dead horse any longer and other than minor tweaking of the power band, to really go further requires more drastic steps.
I don't generally follow the 2.8 buildup threads, but doesn't adding a carb and manifold to the V-6 add a fair amount of power? If that's the case, then either a carb is more effecient than injection, or the engine needs more flow. I doubt if it's the former. You put a lot of work into what you've already done. don't give up on it due to a little setback.
Russ
[This message has been edited by Russ544 (edited 02-28-2004).]
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07:52 PM
Dan010 Member
Posts: 776 From: Katy, Texas USA Registered: Oct 2001
What it actually does is the aftermarket manifolds are much more efficient in the lower areas. Nobody's ever argued that the mid and lower manifolds of the stock Fiero setup were particularly GOOD, I was just trying to get to the pint that the upper was not the limiting factor at all in the system.
John Stricker
quote
Originally posted by Russ544:
I don't generally follow the 2.8 buildup threads, but doesn't adding a carb and manifold to the V-6 add a fair amount of power? If that's the case, then either a carb is more effecient than injection, or the engine needs more flow. I doubt if it's the former. You put a lot of work into what you've already done. don't give up on it due to a little setback.
I really appreciate the work on this dyno test effort. I may just try to get my carb mod dyno'd too. Although my exhaust is a home built 2.5" with only a spark upgrade to go with it.
What I am thinking though, is that with all that work on the intake, was there actually that much more cfm of mixture being delivered thru the ports?
I understand the mods on the main chamber, but would that chamber have been able to deliver more cfm with the existing ports and throttle body?
Bear in mind that the main reason I went to a 390 cfm carb, apart from being an old fashioned guy, was that I was told that the Fiero plenum can only be ported enough to deliver 325 cfm max.
Did this mod job actually increase the mixture delivered to the heads? I believe the injectors are up to the task if they can get enough air.
Arn
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08:34 PM
jstricker Member
Posts: 12956 From: Russell, KS USA Registered: Apr 2002
All we can tell you for certain is that on the last test, at WOT and at the point the engine was making maximum HP, the A/F was over 15:1 with this plenum and at about 12.5:1 with the stock plenum, so yes, it was getting more air in there. How much more POWER that would be worth with different injectors and/or chip setup is debatable, but it was definitely flowing better. One thing I was going to ask Alex to do and absolutely forgot about was to hook up a vacuum gauge and see what it showed during the run. If the gauge was getting close to atmospheric pressure at WOT then the upper was not restricting anymore, all the restriction would be in the lower part. Oh well, live and learn.
John Stricker
quote
Originally posted by Arns85GT:
I really appreciate the work on this dyno test effort. I may just try to get my carb mod dyno'd too. Although my exhaust is a home built 2.5" with only a spark upgrade to go with it.
What I am thinking though, is that with all that work on the intake, was there actually that much more cfm of mixture being delivered thru the ports?
I understand the mods on the main chamber, but would that chamber have been able to deliver more cfm with the existing ports and throttle body?
Bear in mind that the main reason I went to a 390 cfm carb, apart from being an old fashioned guy, was that I was told that the Fiero plenum can only be ported enough to deliver 325 cfm max.
Did this mod job actually increase the mixture delivered to the heads? I believe the injectors are up to the task if they can get enough air.
Arn
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08:41 PM
Alex4mula Member
Posts: 7403 From: Canton, MI US Registered: Dec 1999
John; I can still do that. I can hook up a gage and run it inside and take some readings. What do you think?
stevegibbs; Cam is stock for F-body 3.4.
This is really a hotrod love project for me. I spent about $300 on a pulley and chip on my Harley truck and I got about 45HP and 60lbs TQ. I have spent about 15 times that on this 3.4 and I'm not even close to attain that Oh well...
[This message has been edited by Alex4mula (edited 02-28-2004).]
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09:19 PM
jstricker Member
Posts: 12956 From: Russell, KS USA Registered: Apr 2002
Sure, you can do it anytime. It wouldn't matter if you waited until you changed cams if you left the middle and lower intakes the same, it would still show how much vacuum there was in the upper. One of the reasons I really appreciated you offering to do this was I could tell this was an ongoing thing for you and you weren't afraid to play around with it, which is what it takes to get any meaningful data.
Thanks again for your help.
John Stricker
quote
Originally posted by Alex4mula:
John; I can still do that. I can hook up a gage and run it inside and take some readings. What do you think?
stevegibbs; Cam is stock for F-body 3.4.
This is really a hotrod love project for me. I spent about $300 on a pulley and chip on my Harley truck and I got about 45HP and 60lbs TQ. I have spent about 15 times that on this 3.4 and I'm not even close to attain that Oh well...
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10:08 PM
Scott-Wa Member
Posts: 5392 From: Tacoma, WA, USA Registered: Mar 2002
All we can tell you for certain is that on the last test, at WOT and at the point the engine was making maximum HP, the A/F was over 15:1 with this plenum and at about 12.5:1 with the stock plenum, so yes, it was getting more air in there. How much more POWER that would be worth with different injectors and/or chip setup is debatable, but it was definitely flowing better. One thing I was going to ask Alex to do and absolutely forgot about was to hook up a vacuum gauge and see what it showed during the run. If the gauge was getting close to atmospheric pressure at WOT then the upper was not restricting anymore, all the restriction would be in the lower part. Oh well, live and learn.
John Stricker
Running lean doesn't actually mean it's getting more air... it means it's not getting enough fuel
You should try a scan tool on it and monitor block learn and integrator to see what the system is really doing. Those are short and long term fuel trim and should stay around 128 + or - about 14
If they are higher, the system is attempting to compensate for what it sees as a lean condition, lower it's taking fuel away because it thinks it is to rich. Raising fuel pressure can actually lean the vehicle out... think about how you raise pressure in a garden hose with your thumb or with one of those pressure washers... your raising pressure and lowering volume. With the fuel injectors the pintle becomes the restriction if you raise the pressure to the point where it has a hard time lifting off the seat. To use scan data on a run, monitor O2 voltage (should stay over 800mv WOT) and the fuel trims. If you see the fuel trims are to far away from 128 the modifications that were made to the lookup tables on your chip are wrong. Whoever made the changes should be able to use the fuel trim numbers to adjust the programming if everything else is ok. Also, make sure your MAP has a good vacuum source. I'd put a vacuum gauge on the engine and make sure everything is ok mechanically before doing any program changes to the prom.
Hope this helps
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10:45 PM
PFF
System Bot
jstricker Member
Posts: 12956 From: Russell, KS USA Registered: Apr 2002
Your points are valid but remember we are looking at A/F ratios in pretty much an A/B situation. With the old intake it was running XX, with the new one it was running YY. At WOT, IIRC, the O2 sensor is out of the loop and it's in open loop mode so the tables are controlling the fuel. Since Alex didn't change the tables, but he DID up the pressure, it should have been delivering more fuel at that time and it was still leaner than before according to the A/F graph. This indicates it WAS flowing more air, and the tables needed tweaking (amongst other things).
Johnn Stricker
quote
Originally posted by Scott-Wa:
Running lean doesn't actually mean it's getting more air... it means it's not getting enough fuel
You should try a scan tool on it and monitor block learn and integrator to see what the system is really doing. Those are short and long term fuel trim and should stay around 128 + or - about 14
If they are higher, the system is attempting to compensate for what it sees as a lean condition, lower it's taking fuel away because it thinks it is to rich. Raising fuel pressure can actually lean the vehicle out... think about how you raise pressure in a garden hose with your thumb or with one of those pressure washers... your raising pressure and lowering volume. With the fuel injectors the pintle becomes the restriction if you raise the pressure to the point where it has a hard time lifting off the seat. To use scan data on a run, monitor O2 voltage (should stay over 800mv WOT) and the fuel trims. If you see the fuel trims are to far away from 128 the modifications that were made to the lookup tables on your chip are wrong. Whoever made the changes should be able to use the fuel trim numbers to adjust the programming if everything else is ok. Also, make sure your MAP has a good vacuum source. I'd put a vacuum gauge on the engine and make sure everything is ok mechanically before doing any program changes to the prom.
Hope this helps
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11:18 PM
Feb 29th, 2004
Notorio Member
Posts: 2964 From: Temecula, CA Registered: Oct 2003
Alex never mentioned they were ported, so I assume not, the manifolds were just port matched. I guess the answer to your question is that I can't be sure the middle and lower are more restrictive than the heads, but I doubt it since engines running with the aftermarket manifolds have the capacity to flow a lot more air than the Fiero intake. The person to jump in here would be Oreif, I think, since he's looked into the flows of the heads a lot more than I have.
I wasn't trying to pinpoint the bottleneck with this experiment. I was trying to see if we could shift the powerband higher and remove the top plenum as a source of the problem. I'll leave the rest of the work up to someone else.
John Stricker
quote
Originally posted by Notorio:
I'm not clear on the heads--were they ported or not? How are you sure the other plenums are the bottleneck?
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12:11 AM
Notorio Member
Posts: 2964 From: Temecula, CA Registered: Oct 2003
I do have an AutoXray to monitor things. BLM stays at 128 +/-5. O2 at WOT runs around .850 never dropping below .800. Heads are stock. Thanks to all that appreciate this kind of testing. I wish more people here tested their mods on a dyno to help everybody do the mods that really work. On other forums no one dares to post a hp/tq # without a dyno page. Here is more "seats-of-the-pants" mode which normally is way off. I still would like to see RWHP dyno #s & curve for a 3.4 carbed setup. That would be interesting to compare to a FI engine.
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11:45 AM
sanderson Member
Posts: 2203 From: corpus christi, texas, usa Registered: Sep 2001
O2 at WOT runs around .850 never dropping below .800. Heads are stock.
QUOTE]
Is this volume% oxygen? If so, how could the A/F ratio on the dyno sheet be 17.5:1. I know very little about how a dyno is instrumented. Does it actually measure both air and fuel to get the A/F ratio or is it inferred from other data?
BTW, Kudos to both you and John Stricker for doing this bit of R&D. Definitely one of the most interesting threads I've seen in a while.
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01:37 PM
jstricker Member
Posts: 12956 From: Russell, KS USA Registered: Apr 2002
The A/F had a MAXIMUM of 17.5:1. You have to look at the first graph I posted to see what it was at any given power level. With Alex's original upper, the A/F at maximum HP was ~ 13.4:1 and with the new upper it went to a little over 15:1. For maximum HP most of the time you're looking for A/F ratios of around 12.5:1. Often it's hard to get things sized properly so that you can have the proper mixture at max hp and not have it run too rich down low. This is why the guys that burn the chips and can do it right have people lined up at their doors.
John Stricker
quote
Originally posted by sanderson:
[QUOTE]Originally posted by Alex4mula:
O2 at WOT runs around .850 never dropping below .800. Heads are stock.
QUOTE]
Is this volume% oxygen? If so, how could the A/F ratio on the dyno sheet be 17.5:1. I know very little about how a dyno is instrumented. Does it actually measure both air and fuel to get the A/F ratio or is it inferred from other data?
BTW, Kudos to both you and John Stricker for doing this bit of R&D. Definitely one of the most interesting threads I've seen in a while.
O2 at WOT runs around .850 never dropping below .800. Heads are stock.
QUOTE]
Is this volume% oxygen? If so, how could the A/F ratio on the dyno sheet be 17.5:1. I know very little about how a dyno is instrumented. Does it actually measure both air and fuel to get the A/F ratio or is it inferred from other data?
BTW, Kudos to both you and John Stricker for doing this bit of R&D. Definitely one of the most interesting threads I've seen in a while.
The .800 is referring to the voltage put out by the O2 sensor in the exhaust stream, it is 800 mV, or .800 volts DC. Now here's where it gets complicated. The normal O2 sensor puts out a voltage that's relative to the oxygen content in the exhaust, it is not proportional to the amount of O2. Because of the very narrow range where it is sort of proportional, which is right around the stochiometric air/fuel ratio of 14.7/14.8:1, the factory O2 sensor is used more as a lean/rich indicator switch rather than as a measure of the actual amount of O2 in the exhaust. Once you get much out of this range the sensor is unuseable, that's why the ECM goes to preprogrammed tables at WOT because the engine needs to be run slightly rich at WOT and the O2 sensor doesn't work at that richness. In effect, at WOT the ECM is in open loop and cannot adjust the mixture based on changes in exhaust O2.
The dyno people need to know what the O2 content is outside of the useable range of the factory O2 sensor, so they use what's called a Wideband sensor. It is capable of measuring exhaust O2 amounts that correspond with mixture ratios of around 10:1 to as high as 18:1, sometimes higher. BTW, the V-tec uses a wideband sensor, one of the reasons it is a little more efficient, but at $200/pop those sensors are too expensive for most applications. The A/F ratio on the dyno sheets is calculated using the wideband (WB) O2 sensor readings and shown on the dyno display.
I wouldnt' screw with chips anymore. Get an aftermarket fuel computer, hit a dyno, spend 2 hours on it max, and have the A/F ratio at 12.5:1 across the board when you go WOT. Chips take forever to replace and dyno and just keep having to go back to the dyno many times. I dont' see why you keep wanting to do preprogrammed chips.
At least not in this post. But it will be in a post right after this.
). So I thought maybe that was a big restriction. But like we said, this comparison is between a Darrel's bored TBS/plenum and a bigger plenum and not a totally stock plenum on a 3.4. So I think you can expect at least 5-8HP with this change on a 3.4.
Oh well...
