I would like some help from people who know more than me. I have a Garrett T25 Turbo freshly rebuilt available to me for $100 Unfortunately that's all the info I have on the Turbo at this time and I'm not sure if the seller has much more to offer on it. I also have a 4.9L (no mods) Fiero that would like to go faster.
Ideally I'd like to shoot for between 5-8 psi, but I'm thinking the T25 is going to be too small for the 4.9L. I'd like to confirm with those more knowledgeable and experienced than myself. Suggestions are very welcome as to what Turbo people believe would work and what has. I am well versed on PBJ's build from back in the day, but I haven't seen any documented success stories since then. I know if I want a track destroying monster, I should change engines - I don't want to do that, so just work with me here if you will. Thanks!
Don't even think about the T25 for this application, you could put a potato in the tail pipe and go just as fast. A 60-1 T4 with a .81 turbine housing would be a good start for 10 psi. T3s are too small also.
IP: Logged
03:17 PM
Isolde Member
Posts: 2504 From: North Logan, Utah, USA Registered: May 2008
I've run the map and unless there is a different T57 than the TO4E 57 trim it's to small according to turbocalc. I recently learned that having your peak output rpm in the center island is good for max efficiency, but in terms of performance it is better to be to the right of center at peak output because the further your pressure/rpm points are to the right with good efficiency the quicker the turbo is spooling up relative to a turbo with the pressure/rpm points closer to the left according to a Turbonetics tech I talked to yesterday. It makes sense, the larger the turbo you install on the same platform the further your points on the compressor map start to move to the left or surge line and ofcourse the larger turbo also takes longer to spool up. I did show a T61 and T64 that seemed to be a good match. My understanding is that the 4.9L is not a high rever so I plotted it at 7 psi and 5500 rpm max.
IP: Logged
04:42 PM
Isolde Member
Posts: 2504 From: North Logan, Utah, USA Registered: May 2008
I was plotting it with the HP peaking no higher than 5000, since stock is around 4000. The 215/215 cam that Tajiguy used is definitely all done by 5000, and that cam is more turbo-friendly than the E303, which would peak by 5000 in a 4.9. The 215/215 probably peaks closer to 4500, so it would love the T57. With that 215/215 cam, it's going to be around 230 real HP without boost, even assuming a good exhaust that has no restriction after the turbo, and a no-vacuum intake to the turbo. I like for the turbo to never drop below the 70% efficiency island on the compressor map. The T57 map has more of a U-shape than the 60-1's V-shape, so the lower the boost, the better the efficiency stays. The 60-1 is what Squires Turbo Systems uses as the standard compressor in their rear-turbo kits for the fourth-gen Z28/Formula/TransAm, and those engines start out making a good 300 real HP.
IP: Logged
05:41 PM
1BadGT Member
Posts: 38 From: Portsmouth, VA Registered: Apr 2007
I've been plotting it at 4100 rpm, since that's where it reaches peak HP (and peak torque at 3000 rpm). The goal of this turbo would be to lessen the performance dip once you start reaching higher RPMs. I agree with Joseph that ideally you should plot towards the choke line rather than the surge line.
I've been plotting it at 4100 rpm, since that's where it reaches peak HP (and peak torque at 3000 rpm). The goal of this turbo would be to lessen the performance dip once you start reaching higher RPMs. I agree with Joseph that ideally you should plot towards the choke line rather than the surge line.
Right of center is toward the choke line.
IP: Logged
06:38 PM
Sep 27th, 2009
darkhorizon Member
Posts: 12279 From: Flint Michigan Registered: Jan 2006
I wish to partially alter my last post, because I had the map of a T4E60 marked as being a T4E57. So the T4E57 is too small. But I still insist that the 60-1 is also not an acceptable choice. It doesn't even map at 7 psi until the engine is up to 140 HP N/A, where the T4E60 maps as low as 75 hp N/A, which means it's good several hundred rpm sooner. I made mistakes like that back when I was new to turbocharging, and I have first-hand experience. Always get the turbo that maps the lowest while still meeting your top-end needs. For a 4.9, the 60-1 is not it.
IP: Logged
10:37 AM
1BadGT Member
Posts: 38 From: Portsmouth, VA Registered: Apr 2007
I'm having trouble finding places to map out these turbos you are listing. The Garrett website doesn't seem to be very user friendly towards aftermarket/custom/older applications. What is a reliable site to look up maps and such? Thanks again for the help, I'm sure I'll be back for more in the not too distant future.
IP: Logged
02:49 PM
PFF
System Bot
TiredGXP Member
Posts: 712 From: A cold, miserable place Registered: Jan 2008
I'm having trouble finding places to map out these turbos you are listing. The Garrett website doesn't seem to be very user friendly towards aftermarket/custom/older applications. What is a reliable site to look up maps and such? Thanks again for the help, I'm sure I'll be back for more in the not too distant future.
So, if I understand this correctly, you set the goals with HP, engine size, etc, then find a turbo that runs in the efficient range, while staying away from the surge line, and the pressure ratio tells you what the ratio of ambient to output is at given airflow rate, correct?
IP: Logged
03:35 PM
aaronkoch Member
Posts: 1643 From: Spokane, WA Registered: Aug 2003
You're doing the same thing I am, so I believe it's correct.
I'm looking favorably upon the T4 T04B 60-1 or 62-1, which are also fairly priced and readily available on ebay. I'm curious what I might be overlooking about them; hopefully Isolde can chime in and help me out here.
IP: Logged
03:58 PM
Isolde Member
Posts: 2504 From: North Logan, Utah, USA Registered: May 2008
I've never used that deal before, But the plotting with the red dots is about right, only in that example, it's the wrong compressor. The correct choice of compressor wouldn't have any red dots in any place marked 65% eff. or 60% eff. Lemme look at it again before I type any more. Oh, and BTW, I don't have a compressor map for a 62-1, so I can't comment on a 62-1.
IP: Logged
04:08 PM
Isolde Member
Posts: 2504 From: North Logan, Utah, USA Registered: May 2008
Let's use his plotting. Start by printing it out, then get a fine-tip pen and a straightedge. Now, number across the top to match the numbers underneath. Then run a straight line from 15 at the bottom to 30 up on top. Notice it runs right square through the fourth red dot. Notice this dot is not on the 70% island. But since it is the left-most dot at the desired pressure ratio, we can get some use from it. Even more so since it happens to fall on the line you just drew. What this tells us, well, those of us who learned this before your computer tool, is that this turbo doesn't even map until the engine gets to 150 HP Naturally Aspirated. Now, moving on, notice the sixth red dot is again off the 70% island. But that's fine since the 3800-2 with porting and cam and headers is still below 250 HP N/A. Tonight I'll hand-map this engine on a few different compressor maps and see what would be best. I'm really not clear on the computer tool thing, because the correct approach, based on decades of expensive experience, is to correct for elevation while plotting your cengine on different maps. You don't want to have problems if you do take the car to sea level, do you? You plot the correction so your map has 2 sets of red dots on it. Think of it as figuring in the allowance for density-altitude. See, different weather can affect the barometric pressure, and just because your elevation should figure 13.8 instead of 14.7 doesn't mean that that's always dead on. I'll scan my results in tomorrow to illustrate for you.
IP: Logged
04:27 PM
Isolde Member
Posts: 2504 From: North Logan, Utah, USA Registered: May 2008
oops. my damned ADD. Something felt wrong, and I just saw what. Go back to your printout. Run a straight line across the fourth through eighth red dots. , then number up the right side to match the left. Then run a line across at 2.00. Now we can do the reading. So, run your straightedge vertically, and mark your 2.00 line where it intersects 22.5. Now, at the bottom, make a mark halfway between 10 and 12.5. Now pull a straight line from that mark to the last one. Now we see where I just goofed in my last post. This compressor maps this engine when this engine is making 115 hp. Better, but still not great. Even better is possible. But this turbo is too small for a 3800 Series 2at this boost level. It's not good to 250 N/A HP, after all. Why post a map that goes past 2.00? It screws me up. You can't run over 2.00 on pump gas. Anyway, this turbo won't even support this engine's stock 205 peak HP at this boost level. nyway, as I typed, I'll hand plot this tonight and scan it up for you to see. Screw trusting a computer program. That's worse than having to redo the hand plotting because of my ADD.
IP: Logged
04:40 PM
TiredGXP Member
Posts: 712 From: A cold, miserable place Registered: Jan 2008
I think you've got to enter some VE and temperature numbers based on the 4.9 and the efficiency of the IC you plan to use. The VE numbers that default into the calculator are probably a fair bit too high for a 4.9 (certainly too high for a GEN I 60*V6!)
This site has a VE estimator (based on stock peak torque and peak HP): http://www.megamanual.com/v22manual/vetable.htm You may have to do some interpolation of the output to find the RPM points to plug into the turbo calculator.
You don't need VE for the correct, non-computer method, nor do you need displacement. Those don't truly matter the least bit. Turbos are a question of lbs of air. And you can get that from HP and RPM.
IP: Logged
05:12 PM
1BadGT Member
Posts: 38 From: Portsmouth, VA Registered: Apr 2007
I think I'm getting somewhere on an educated guess to what turbo would be ideal. However, I'm having difficulty plotting and understanding the "power curve" of the turbo, like where it starts to kick in as far as HP/RPM.
To my understanding, I don't want maximum boost too early as the compression ratio is already fairly high in the 4.9L (9.5:1). I'm thinking I wouldn't want maximum boost until ~3500 RPM.
You guys are a big help so far, I'll be sure to let you know what I decide to go with and get a build thread up if I'm ever successful.
IP: Logged
05:35 PM
PFF
System Bot
darkhorizon Member
Posts: 12279 From: Flint Michigan Registered: Jan 2006
the squirrel calculator does NOT come even close to what my turbo actually does on my car. Its a good ballpark method, but I would not plan a turbo build off of their suggestions alone.
What it really comes down to, is deciding what you want your HP to be, and pick a turbo that flows it around the PSI level you think you be at. Get an idea for maximum lb/m you want to be flowing, and look at turbos that fit the bill at the PSI rating you will be at.
I still say that if you plan to stay sub 400whp, a HX35 will be cheap and easy.
IP: Logged
05:45 PM
1BadGT Member
Posts: 38 From: Portsmouth, VA Registered: Apr 2007
I'm definitely looking to stay modest with this. I'm not really looking for much more than 300whp. I'll see how I like that at the track and go from there. I'm looking at keeping the engine mostly stock, with maybe work on the top end.
So with that said, I'm looking for about 300whp @ 5-8 psi. It looks like I'll need 35-40 lb/m for that, correct me if I'm wrong.
I've been checking out the HX35, but it looks as though I can get a T04B cheaper and easier. According to what I think I need, the T4 T04B 60-1 or 62-1 look pretty good.
IP: Logged
06:01 PM
TiredGXP Member
Posts: 712 From: A cold, miserable place Registered: Jan 2008
You don't need VE for the correct, non-computer method, nor do you need displacement. Those don't truly matter the least bit. Turbos are a question of lbs of air. And you can get that from HP and RPM.
But you still have to get that airmass into a combustion chamber. VE and displacement define how much air can flow in the engine, and are key in determining the pressure ratio needed for the desired airflow/power. In other words, you have to assess the compressor map in the context of engine's ability to breath. Your way may work, I just prefer to do the math.
1BadGT - you may have found it already, but if not, I suggest that you read the Garrett TurboTech 1, 2, and 3 webpages: http://www.turbobygarrett.c...r/turbo_tech101.html Lots of good info about basic turbo operations and selecting a compressor matched to your engine and performance objectives.
Cheers
IP: Logged
06:13 PM
1BadGT Member
Posts: 38 From: Portsmouth, VA Registered: Apr 2007
But you still have to get that airmass into a combustion chamber. VE and displacement define how much air can flow in the engine, and are key in determining the pressure ratio needed for the desired airflow/power. In other words, you have to assess the compressor map in the context of engine's ability to breath. Your way may work, I just prefer to do the math.
1BadGT - you may have found it already, but if not, I suggest that you read the Garrett TurboTech 1, 2, and 3 webpages: http://www.turbobygarrett.c...r/turbo_tech101.html Lots of good info about basic turbo operations and selecting a compressor matched to your engine and performance objectives.
Cheers
Yep, I've read those several times and reference them continually in this search. I also have an older book on turbos from Hugh MacInnes that has a bit more detail than the Garrett site.
Considering all the factors, I may fall quite short of the 300whp without some major tuning, but we'll see what can be done about it when I get there. I appreciate all the help.
IP: Logged
06:18 PM
Isolde Member
Posts: 2504 From: North Logan, Utah, USA Registered: May 2008
have any of you got the latest version of that Corky Bell book on turbocharging? I'm in agreement with Corky that you should understand what you're seeing instead of relying on someone else, or in other words, a computer program, to figure it out for you. I'm old school, and I'm not up on the latest programs, but I'm not beyond my usefulness, or my ability to get the best possible results without unnecessary complications. Only input the numbers needed to get THE solution. And I'll lay the standard $100 cash on the E60 being far superior to the 60-1.
IP: Logged
06:53 PM
1BadGT Member
Posts: 38 From: Portsmouth, VA Registered: Apr 2007
Just so I'm not making an assumption, when you say "E60" do you mean the T04E 60 trim?
I totally agree with you on the fact I should know what I'm dealing with, but getting info from the outside is helping me fill in the gaps a little bit quicker. I don't intend to do anything in this project without fully understanding it. Having a fast car is one thing, but knowing why it's fast and how much more you can get out of it is another thing entirely.
[This message has been edited by 1BadGT (edited 09-28-2009).]
IP: Logged
07:11 PM
TiredGXP Member
Posts: 712 From: A cold, miserable place Registered: Jan 2008
Before I found the Squirrel Performance calculator, I built a spreadsheet based on the formulas on the Garrett website. Virtually identical results (in terms of airmass and pressure ratio) are provided by the Squirrel calculator. The real benefit of that site is its ability to plot airflow on the various compressor maps.
Maximum Boost (by Corky Bell) is out there as an Adobe file on various torrent sites. Its a pretty good read, and covers a number of installation issues such as oiling, control systems....
My biggest frustration is that nothing I've read yet really covers selecting a turbine. At least Corky Bell provides some "rules of thumb" on this subject.
Before I found the Squirrel Performance calculator, I built a spreadsheet based on the formulas on the Garrett website. Virtually identical results (in terms of airmass and pressure ratio) are provided by the Squirrel calculator. The real benefit of that site is its ability to plot airflow on the various compressor maps.
Maximum Boost (by Corky Bell) is out there as an Adobe file on various torrent sites. Its a pretty good read, and covers a number of installation issues such as oiling, control systems....
My biggest frustration is that nothing I've read yet really covers selecting a turbine. At least Corky Bell provides some "rules of thumb" on this subject.
Cheers
I just won a remanufactured Garrett Ball bearing 60-1 on Ebay for a very good price. Turbonetics was going to sell me a remaned T66 for $500 but the rep didn't email me the info he said he would and I wound up saving more than $100 as a result. I copied the picture below from a car magazine article but I'm not sure which one. It will give you some idea on a turbine housing selection. Isolde you're not past your usefulness but you can add to your arsenal of knowldege with computer programs. The trend I've seen as far as efficiency is that it can indeed affect your turbo choice because the compressor points move when efficiency changes so it probably should be considered when deciding on a turbo.
IP: Logged
08:12 PM
1BadGT Member
Posts: 38 From: Portsmouth, VA Registered: Apr 2007
I don't want to seem arrogant to disregard your advice, but everything I'm finding on the T04E 60 seems a bit small. It looks like it'd be quick to spool and kick in, it might be perfect, but I think it's going to be a little small for what I have in mind. I think I still prefer the T04B 60-1 since it has a bit more to give than the E60 (assuming we're looking at the same one) even though it'll be slower to kick in. I intend to be able to use this same setup should I decide to push it beyond 8 psi and into even more dangerous and uncharted territory.
edit: I hope you can understand that, I barely did myself after reading it...
[This message has been edited by 1BadGT (edited 09-28-2009).]
IP: Logged
08:35 PM
TiredGXP Member
Posts: 712 From: A cold, miserable place Registered: Jan 2008
Originally posted by Joseph Upson: I just won a remanufactured Garrett Ball bearing 60-1 on Ebay for a very good price. Turbonetics was going to sell me a remaned T66 for $500 but the rep didn't email me the info he said he would and I wound up saving more than $100 as a result. I copied the picture below from a car magazine article but I'm not sure which one. It will give you some idea on a turbine housing selection....
Interesting chart - fairly consistent with what I eventually bought for the 3.1 - a T3 turbine with .82 AR and a 50 trim T04E compressor.
As far as the 4.9 goes, I would have thought that a compressor similar to one of: T04B 62-1 trim, GT3582R (56 trim), or a T61 might work given the fairly low boost requirements and low revving nature of the engine.
IP: Logged
09:59 PM
PFF
System Bot
darkhorizon Member
Posts: 12279 From: Flint Michigan Registered: Jan 2006
It seems the more I learn about this, the less I know.
I'm getting a little confused on turbine A/R / trim. I was looking at a T3/T4 hybrid (T04B V1/V2 I think) and the A/R was .63 with 73 trim. Am I correct in thinking that a smaller A/R will be beneficial to the lower revving 4.9L or should I still stick with a larger A/R (.90 +) for higher range power as is the standard practice. I might be over-thinking all of this.
edit - For clarification I'm looking to improve 1/4 mile times rather than max speed. I'm looking to get the car in the 12's with some tuning.
[This message has been edited by 1BadGT (edited 09-28-2009).]
Don't even think about the T25 for this application, you could put a potato in the tail pipe and go just as fast. A 60-1 T4 with a .81 turbine housing would be a good start for 10 psi. T3s are too small also.
one yes you are correct but two could work small T3 would be better esp for a street car twins will kick in earlier and that really helps on the street and I would question if a 4.9 caddy can use 10psi and LIVE LONG esp at near top RPM's where a big turbo makes top power
------------------ Question wonder and be wierd are you kind?
IP: Logged
11:22 PM
Sep 29th, 2009
TiredGXP Member
Posts: 712 From: A cold, miserable place Registered: Jan 2008
It seems the more I learn about this, the less I know.
I'm getting a little confused on turbine A/R / trim. I was looking at a T3/T4 hybrid (T04B V1/V2 I think) and the A/R was .63 with 73 trim. Am I correct in thinking that a smaller A/R will be beneficial to the lower revving 4.9L or should I still stick with a larger A/R (.90 +) for higher range power as is the standard practice. I might be over-thinking all of this.
edit - For clarification I'm looking to improve 1/4 mile times rather than max speed. I'm looking to get the car in the 12's with some tuning.
What's the redline on your 4.9 anyway? I didn't think they ran much over 5000 rpm.
You're correct, smaller AR on the turbine spools quicker. But since the 4.9 makes tons of torque at low rpm's anyway, you'd probably be better off with a larger Turbine AR to avoid too much back pressure at higher RPM.
Cheers
IP: Logged
12:16 AM
1BadGT Member
Posts: 38 From: Portsmouth, VA Registered: Apr 2007
Originally posted by ray b: one yes you are correct but two could work small T3 would be better esp for a street car twins will kick in earlier and that really helps on the street and I would question if a 4.9 caddy can use 10psi and LIVE LONG esp at near top RPM's where a big turbo makes top power
I run twin T3s on the 3.9L, a nice idea but simple = reliable that's why I'm switching to a single turbo and one T3 is not enough for the 3.9L given the limited turbine housing size available and even with a low rpm max of 5200 rpm it certainly would choke a 4.9L. I started with turbos in the early 90s and actually put a T25 on a 2.8L to learn quickly it was a bad idea. The T25 used on the Turbo Grand Prix 3.1L was to small. The turbo Ford ~2.3L and some Chrysler 2.2L used a single T3 .60/.63 so the 1.15 series T3 turbine would be borderline at best for a 4.9L. I'm just using a rough estimate. I used two different programs for the boosted simulation and single T3 compressor maps didn't come close to reasonable for 4.9L.
IP: Logged
02:45 AM
fieromadman Member
Posts: 2217 From: Oconomowoc WI, USA Registered: Jan 2003
Thanks to all the help. I've figured out the entire build now. I'm going for the T04B 62-1, 38mm Wastegate, BOV, Saab 900 intercooler, with Megasquirt 2 to manage everything computer from fuel injection to boost to knock sensor. I think I had to choose the Megasquirt because I still require the stock caddy ECM for the 4t60e tranny. Regardless, I think Megasquirt will be about as fun as the turbo to me personally.
Again thanks for all the help and keep an eye out for build threads from me. I think I'll start with the Megasquirt in mid-October.
IP: Logged
03:16 PM
Fieroseverywhere Member
Posts: 4242 From: Gresham, Oregon USA Registered: Mar 2006
What's the redline on your 4.9 anyway? I didn't think they ran much over 5000 rpm.
You're correct, smaller AR on the turbine spools quicker. But since the 4.9 makes tons of torque at low rpm's anyway, you'd probably be better off with a larger Turbine AR to avoid too much back pressure at higher RPM.
Cheers
Stock programmed redline on the 4.9 is 5252 (fuel cut off). The limiting factor in a stock 4.9 is the 4t60e shift points set up in the PCM. They don't allow the motor to rev above 5000 (actually 4800 IIRC). However the 4.9 can rev to 6000 on stock valve train with the fuel cut off limit moved. In stock form they just don't make much power up there so without the other mods there really is no point. They do a little better with a cam re-grind. Adding a turbo though...
Going higher then 6k requires valvetrain mods which most 4.9 guys know don't exist in a bolt on form. There are options out there but require a good amount of custom head work which is pretty cost prohibitive unless you can do it yourself. New valve springs, cam and possibly rockers are in order at the very least. Mine currently revs to 5600 easily and makes decent power there with only a mild cam.
