Watching another thread on using multiple throttle bodies (on V-6) has rekindled an old idea that's been rattling around in my brain for a few years. I've been thinking it would be very cool to build a manifold for the Northstar and mount 8 small TB on it, looking something like the old Hilborn injection. a TPS on just one TB should be all that's required to use a 7730 ECM. I was thinking of a very shallow plenum under the TBs to help ballance the flow. what do you think Ryan? any math guys out there that can help me out on a size to shoot for on the TBs? anyone haveing thoughts on this idea, good or bad, I'm interested in listening.
I think it's a great idea (as long as I don't have to be the one to figure out all the issues ) Even if turns out to do absolutely nothing for performance, it would still look great at shows. Post pics of progress
No need for a plenum if you have equal length runners. All you need then is a connection between all 8 for a vacuum block, etc. Check out ITB setups for small block Chevies. The intake design should be the same - just tune it for your displacement and power band.
Will wanted to do this with throttle bodies from a couple motorcycles.
Then you just have to build an adapter between them and the N* port layout.
A "plenum" can be as simple as a box with tubes from each TB going to it. Doesn't have to be big. Just enough to smooth out the pulses.
ITB's don't have to worry so much about oversizing and turning the gas pedal into an on-off switch. 40-50mm throttles would probably be fine
What I envision would be a flange bolted onto each N* head with a...... 2"? curved piece coming off of it. this curved piece would contain the injectors. above/between them would be a "box", only about an inch deep, covering all 8 ports. then roughly above each head port would sit a TB. one of which would have a TPS on it. It doesn't _seem_ to difficult to me, but then again... ignorance is bliss.
Are you still setting up the 7730s or some similar variant? I might want another one from you before too long as I'd be using another N* "mule motor" that I have, to experiment with on this setup. My current IMSA N* with your ECM is running awsome BTW.
Originally posted by Russ544: What I envision would be a flange bolted onto each N* head with a...... 2"? curved piece coming off of it. this curved piece would contain the injectors. above/between them would be a "box", only about an inch deep, covering all 8 ports. then roughly above each head port would sit a TB. one of which would have a TPS on it. It doesn't _seem_ to difficult to me, but then again... ignorance is bliss.
Are you still setting up the 7730s or some similar variant? I might want another one from you before too long as I'd be using another N* "mule motor" that I have, to experiment with on this setup. My current IMSA N* with your ECM is running awsome BTW.
Russ
I guess I don't follow. The throttle bodies all sit on a common plenum? You would be losing out on the benefits of ITB's.... Air from 1 throttle body would be feeding other cylinders. You wouldn't be able to use large throttles. To get the maximum benefit, you want each cylinder to be separated. Drill a vacuum port into each TB and run a hose into a small 3"x3"x1" plenum for the MAP.
I guess I don't follow. The throttle bodies all sit on a common plenum? You would be losing out on the benefits of ITB's.... Air from 1 throttle body would be feeding other cylinders. You wouldn't be able to use large throttles. To get the maximum benefit, you want each cylinder to be separated. Drill a vacuum port into each TB and run a hose into a small 3"x3"x1" plenum for the MAP.
Ya that's true. perhaps I'm just thinking about it too much, but I'm thinking that the vacume signal would just be too pulsed with a vacume line fed mini plenum to get a good signal for the MAP, and might also have conflicts when using the PB booster. power isn't actually the object of this endevor. in fact if it had the same power as a single TB and be reasonably smooth running that would be excellent .
The GSXR TB setup does look promising, but would require (by me) that they be cut apart due to spacing. as near as I can find, they have 42MM throtle plates, which is ok, but the spacing is about 80 mm apart. the N* ports are about 100mm apart, so over the spread of all four tb that gets a little dicy for equal length runners. cost is certanly a factor however, so these are the tb of choice at the moment.
thanks for all the input so far,
Russ544
[This message has been edited by Russ544 (edited 11-04-2007).]
There's an article about motorcycle & jetski/snowmobile throttles in www.msefi.com under the airflow section. I have two sets of 98-99 GSXR 750 throttles. They're about 44 or 45mm, IIRC. I have spaced the throttles out, and know how to deal with the linkage, but haven't done it yet. Most modern motorcycle throttles have a secondary set of blades that is actuated by vacuum controlled by the ECM. These are to aid low speed driveability and must be removed (and the shaft bores sealed) before they can be used on a car engine.
The difficult part of using these throttles on a Northstar is dealing with the cylinder head interface. The way Bubbajoe did it is NOT a good way... The centerline of the intake ports is at a significant angle relative to the mounting surface of the intake manifold, so in order not to have a discontinuous transition from the runner to the port, the tube must go through the plate at an angle, and be swedged from round to rectangular at the same time...
[This message has been edited by Will (edited 11-04-2007).]
There's an article about motorcycle & jetski/snowmobile throttles in www.msefi.com under the airflow section. I have two sets of 98-99 GSXR 750 throttles. They're about 44 or 45mm, IIRC. I have spaced the throttles out, and know how to deal with the linkage, but haven't done it yet. Most modern motorcycle throttles have a secondary set of blades that is actuated by vacuum controlled by the ECM. These are to aid low speed driveability and must be removed (and the shaft bores sealed) before they can be used on a car engine.
The difficult part of using these throttles on a Northstar is dealing with the cylinder head interface. The way Bubbajoe did it is NOT a good way... The centerline of the intake ports is at a significant angle relative to the mounting surface of the intake manifold, so in order not to have a discontinuous transition from the runner to the port, the tube must go through the plate at an angle, and be swedged from round to rectangular at the same time...
that link has some very usefull info. thanks.
I don't see any particular problem with the head to injector interface. I've build several sets of headers which would be the same method I was concidering. If that's the most difficult part.... I'd be in great shape on this project
What's your thoughts on the problems related to vacume signal for the PB, MAP, etc.?
Russ
[This message has been edited by Russ544 (edited 11-04-2007).]
Originally posted by Russ544: I don't see any particular problem with the head to injector interface. I've build several sets of headers which would be the same method I was concidering. If that's the most difficult part.... I'd be in great shape on this project
What's your thoughts on the problems related to vacume signal for the PB, MAP, etc.?
Russ
Not sure if we're on the same channel, here. WRT building the flanges & tubing... The tubing has to go through the flange at an angle in order to maintain smooth transitions in port walls and cross sectional area. Where it goes through at an angle, it ALSO has to transition from (presumably) round to the rectangular shape of the N* intake port. If you're saying that's ok, then that's OK, but what you've said so far in this thread hasn't acknowledged those difficulties.
I think the setup would be fine with a small vacuum box hooked to each throttle via a small tube. The throttles I have each have two vacuum ports. I was planning to run one port on each throttle to a vacuum reservoir which would "supply" the car's vacuum accesories that require "flow" such as the brake booster, cruise, wastegate solenoid, etc. The other port in each TB would go to a very small plenum that would drive things that require "signal" like the MAP sensor, boost reference, etc. That way Bernoulli effects due to the dynamic pressure of flowing gas in the vacuum manifolding wouldn't affect MAP sensor readings. Check valves in the "flow" system might be necessary to keep one cylinder from pulling air from another cylinder's runner and depleting reservoir vacuum, but I don't think it would be a problem for the "signal" system, since the lines would be smaller and the potential flow problem much smaller.
Does anyone have a drawing or picture of the head port layout? What approximate angle (relative to the head-intake surface) does the port enter?
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I haven't measured, but I would toss off 30 degrees from perpendicular as an initial estimate... Can measure this weekend.
That means that if the runners are installed perpendicular to the flange, there will be an abrupt 15% drop in port CSA across the flange... bad for performance...
Does anyone have a drawing or picture of the head port layout? What approximate angle (relative to the head-intake surface) does the port enter?
hard to see in the pic, but it's about 20* to the valve head center.
I agree with Will that it would certainly be benificial to have the manifold port line up with the angle of the head port, but where we apparantly dissagree is just how hard that would be to accomplish. I really don't see the problem in fabrication. If for some reason (like linkage design perhaps?) it was benificial to have the tb sit straight up you could still set them inbord somewhat and use curved runners down to the head ports.
So then mill the intake ports open a bit. CHRF enlarges the intake ports by 0.1" all the way around on their P&P heads.
That doesn't change the angle at which the port crosses the interface.
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Originally posted by Russ544: I agree with Will that it would certainly be benificial to have the manifold port line up with the angle of the head port, but where we apparantly dissagree is just how hard that would be to accomplish. I really don't see the problem in fabrication. If for some reason (like linkage design perhaps?) it was benificial to have the tb sit straight up you could still set them inbord somewhat and use curved runners down to the head ports.
Russ544
If you don't think it's an issue, go for it. It's quite doable, just not nearly as simple as "butt pipe to flange, weld". What I'm looking at is the combination of angle and odd shape. My throttles have round outlets, so I'll need round runners to butt up to them, but the runners will have to be shaped oblong going through the flange. I don't think it would be very hard if using rectangular tubing. I'm looking at KISS. You said you'd like to weld your injector bungs into your runners, I'd like to use the injector bungs that are already in my throttles, which means that I'd have to maintain the Caddy injector targetting and the adapters between the heads and throttles would have to be very short.
Oh come on now Will. the KISS theory isn't even IN your dictionary, vocabulary, or thought process (I've seen your N* rebuild thread) J/K
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If you don't think it's an issue, go for it.
I accept your challenge I've spent the morning getting set up with Paypal and E-bay so I can purchase some items to get this project on the road (and enter the current century, technology wise ) I've got a little work left to do on my sbc project, but I'll also be stripping down an extra N*block and head set I have, to use to mock up this whole mess. this should proove to be an interesting excersize. I look forward to the challenge !! I may initially use the Holley Commander ECM that's been gathering dust in my shop for this project. I have it... so I may as well get some use out of it.
Originally posted by Russ544: Oh come on now Will. the KISS theory isn't even IN your dictionary, vocabulary, or thought process (I've seen your N* rebuild thread) J/K
Ok, ok... maybe "Occam's Razor" then...
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I may initially use the Holley Commander ECM that's been gathering dust in my shop for this project. I have it... so I may as well get some use out of it.
Russ544
I've been curious about whether or not that computer really is as bad as people say it is... I've seen a Haltech interface and think that's hopelessly primitive, but it should have what's necessary...
Occam's razor..... a much more complex way of rationalizing a simple solution...... I like it
The Holley is actually ok in many ways. If a guy was really tuned into EFI and the Holley itself I'm sure it would get the job done just fine. My brain just works more like a Stromberg carburator than a Wii computer. I had my N* running and driving pretty well with the Holley, but I just never did get it dialed in that last 5% so that it ran _really_ well. being able to tune the ECM will actually be a great advantage on the itb setup though I imagine. + I already have it
Russ
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Originally posted by Will:
I've been curious about whether or not that computer really is as bad as people say it is... I've seen a Haltech interface and think that's hopelessly primitive, but it should have what's necessary...
, I'd like to use the injector bungs that are already in my throttles, which means that I'd have to maintain the Caddy injector targetting and the adapters between the heads and throttles would have to be very short.
very short indeed if you want to maintain targeting. in fact I'd say you'll need to have the TBs sitting angled in to match the head port angle and the inner edge right on the head flange. Do you think it critical that the injectors are located precicely as the original Cad? I have mixed feelings about that when I see TBI setups that work fine when sprayed a foot away from the ports.
TBI injectors operate at much lower pressures and have much wider spray patterns than port injectors. This works in conjunction with manifold turbulence to give good atomization of the mixture by the time it gets to the cylinder. Targeting is much more important for port injectors because of their higher velocity, more concentrated spray patterns.
LS1's, for instance, have their injectors targeted such that they spray directly on the back of the intake valve. This cools the valve and uses valve heat to help vaporize fuel on its way into the cylinder. If you move the injector, you lose this benefit. This probably won't affect peak power at all, but probably will affect fuel mileage and part throttle emissions (don't roll your eyes at the mention of emissions... a clean running engine is a happy engine).
Some of the gains of precise injector targeting go hand in hand with sequential injection, though... so if you go with a batch fire computer, you throw those away anywho...
I spent much of the day today stripping down the 2 spare N* longblocks that I have, to see what I have to work with. I have a 97 vinY and a 98 vin9. the vin 9 was a dissapointment as it has some surface rust forming in several cylinders and someone has pulled the pan and removed 2 rod caps, which are missing. the crank looks excellent, so I don't know what the story was here. no biggie as I only paid $75.00 for that one. the vin Y motor looks really good however. very little sign of wear anywhere. the chain tensionors are like new, so it must be pretty low miles. I'll do a de-carbon and valve job and install the vin9 cams/lifters in it. the bare vin 9 is now a jig to make my manifold on
I won the ebay bid on one GSXR 600 injector set today, and I'm current high bidder on another one, so things are starting to roll.
I also made a little adaptor to re-install the valve spring keepers on this thing. I just milled a window in the side of a piece of aluminum tubing and countersunk a relief in one end to locate the spring keeper. by using a regular c type valvespring compressor, along with this adaptor, replacing the split locks is reasonably easy now.
[This message has been edited by Russ544 (edited 11-09-2007).]
As with motorcyle engins using 1 carb or TB/cylinder, they need to be turned precisely with all interconnecting vacuum lines blocked off. Personally, I dont think it would be worth the trouble, whereas if just one TB goes a lil too far out of adjustment the whole concept is kind of wasted. I've had Monza with one carb/cylinder, a few bikes with the same, and now 124 spider with 4 carbs and they just dont like to stay in tune. More ent always better, sometimes it's just PIA.
As with motorcyle engins using 1 carb or TB/cylinder, they need to be turned precisely with all interconnecting vacuum lines blocked off. Personally, I dont think it would be worth the trouble, whereas if just one TB goes a lil too far out of adjustment the whole concept is kind of wasted. I've had Monza with one carb/cylinder, a few bikes with the same, and now 124 spider with 4 carbs and they just dont like to stay in tune. More ent always better, sometimes it's just PIA.
The only "adjustment" to an EFI system is the timing of the throttles to make sure that they all open at the same time... Once that's set, it won't creep.
Originally posted by Russ544: I'll do a de-carbon and valve job and install the vin9 cams/lifters in it.
The lifters are the same... it's the valvesprings that are different. You MUST upgrade the VIN Y springs if you want to spin over 6400 RPM. The VIN 9 springs are good for 6700, but NO MORE.
Originally posted by Francis T: As with motorcyle engins using 1 carb or TB/cylinder, they need to be turned precisely with all interconnecting vacuum lines blocked off. Personally, I dont think it would be worth the trouble, whereas if just one TB goes a lil too far out of adjustment the whole concept is kind of wasted. I've had Monza with one carb/cylinder, a few bikes with the same, and now 124 spider with 4 carbs and they just dont like to stay in tune. More ent always better, sometimes it's just PIA.
They're not carbs.
Actually I think multiple throttle bodies is probably better from a tuning perspective. On sequential motors, all of the cylinders have individual fuel trims for idle and off idle. On the LT1, some cylinders needed _some percent_ more fuel than the rest to be "in tune" due to air flow differences in the intake. With ITB's, you eliminate the potential of one cylinder stealing another cylinder's air. So rather than dialing in the average "best tune", where one cylinder could be really lean, and one really rich..... they all move together and have less difference between cylinders.
That and more stable manifold pressure. MAP systems have trouble with big cams and idling (still better than with a carb) because the manifold pressure at idle isn't stable. This is because (at least with a V8), the cylinder in the middle of its intake stroke (peak "pull") can pull exhaust gas from the next cylinder in the firing order, which is just beginning its intake stroke and has very little pull. When the throttle plates are closed, this is actually the path of least resistance for gas to get into the cylinder. This is a big problem on single plane/single plenum manifolds (less so with EFI manifolds like the LS1's with longer runners), not as big a problem with dual plane manifolds and not a problem at all with throttle per cylinder.
As long as you have your VE tables dialed in and your IAT compensation curve correct, the only seasonal change for which your BLM's will have to compensate is humidity. Everything else (altitude, engine temp, time at WOT, ec) should all be compensated in the ECM.
I agree, they are not carbs or as finicky. Yes, they will all move at the same time and yes the throttle plate is the only thing that must move the same amount at the same time for each. That's still a lot linkage and throttle bushings to wear and they will. Can it work greeat, sure. I guess I'm from the old 'KISS' school of thinking, KISS as in 'Keep It Simple Stupid.' More moving parts the more areas for eventual problems, although todays (most anyway) TBs are lot better made then yesterdays carbs so maybe it's worth trying.
The lifters are the same... it's the valvesprings that are different. You MUST upgrade the VIN Y springs if you want to spin over 6400 RPM. The VIN 9 springs are good for 6700, but NO MORE.
I always keep very close track of which lifters come off which lobe of a cam. the vin 9 cam/lifters will go in just as it came out. I also kept the springs separated and tagged, although I'll be darned if I can tell any difference in any of them. are the vin 9 springs supose to be longer, bigger wire, or marked in some way? are the intake and exhaust springs both different than the vin Y, or just the intake?
There are a LOT of valves to deal with on this thing 1/2 way home:
my jury rigged valve spring keeper- holder- retainer- thingy worked really well. a dab of grease on the tip of a screwdriver holds the split locks for installation:
I agree, they are not carbs or as finicky. Yes, they will all move at the same time and yes the throttle plate is the only thing that must move the same amount at the same time for each. That's still a lot linkage and throttle bushings to wear and they will. Can it work greeat, sure. I guess I'm from the old 'KISS' school of thinking, KISS as in 'Keep It Simple Stupid.' More moving parts the more areas for eventual problems, although todays (most anyway) TBs are lot better made then yesterdays carbs so maybe it's worth trying.
Of course I can't speak for Wills motives, but for my own I think you may have the wrong inpression of why I'm doing this in the first place. being practical isn't even in the equation . I enjoy the mental and physical challenge of this type of thing, and it's only intended to be: entertaining to build and, (if it actually works), worth a point or two at shows. if it was practical it wouldn't be any fun at all .
Russ
[This message has been edited by Russ544 (edited 11-10-2007).]
Of course I can't speak for Wills motives, but for my own I think you may have the wrong inpression of why I'm doing this in the first place. being practical isn't even in the equation . I enjoy the mental and physical challenge of this type of thing, and it's only intended to be: entertaining to build and, (if it actually works), worth a point or two at shows. if it was practical it wouldn't be any fun at all .
I believe the Vin 9 has fewer coils to create the stiffer spring rate.
interesting........... I just went out and checked a couple dozen springs and they are all the same. my vin 9 and vin Y springs all have the same number of coils. the height and the wire mikes the same as well. I even miked my cams and I deffinetly have one vin of each variety. I wish I had a spring tester here, as I'm really curious now.
Of course I can't speak for Wills motives, but for my own I think you may have the wrong inpression of why I'm doing this in the first place. being practical isn't even in the equation . I enjoy the mental and physical challenge of this type of thing, and it's only intended to be: entertaining to build and, (if it actually works), worth a point or two at shows. if it was practical it wouldn't be any fun at all .
) Even if turns out to do absolutely nothing for performance, it would still look great at shows. Post pics of progress 
