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Just look at some of the port EFI systems that GM used. GM started with the TPI with what, like 17" or 19" long runners to get more low end torque out of the crappy 80's era low performance engines. Then, GM came up with the LT1 intake with the quite short runners around 3" long. Then, they went longer again on the LS engines, something like 11" give or take depending on the intake. So, GM's current thinking is that longer runners are beneficial compared to short runners. This directly contradicts any claims that the runner length doesn't matter and I put more faith in the millions of dollars GM has spent on R&D over what any aftermarket company says.
I ran a TBI system on a Performer intake and it worked fine, great low end power, clean plugs, good idle, etc. Must have been TBI that was too old though, instead of this newfangled TBI that can't work on a dual plane.
I don't put much faith in FAST. They had (or still have??) lots of trouble making their electronics work in a car, along with lots of excuses about how their customers are causing the issues by their poor installation.
Just look at some of the port EFI systems that GM used. GM started with the TPI with what, like 17" or 19" long runners to get more low end torque out of the crappy 80's era low performance engines. Then, GM came up with the LT1 intake with the quite short runners around 3" long. Then, they went longer again on the LS engines, something like 11" give or take depending on the intake. So, GM's current thinking is that longer runners are beneficial compared to short runners. This directly contradicts any claims that the runner length doesn't matter and I put more faith in the millions of dollars GM has spent on R&D over what any aftermarket company says.
I ran a TBI system on a Performer intake and it worked fine, great low end power, clean plugs, good idle, etc. Must have been TBI that was too old though, instead of this newfangled TBI that can't work on a dual plane.
I don't put much faith in FAST. They had (or still have??) lots of trouble making their electronics work in a car, along with lots of excuses about how their customers are causing the issues by their poor installation.
Yep. TPI was 25.375" long runners from the runner entry to the valve; they were also very small inside diameter tube @ 1.47" ID. (The intake wave tuning is primarily based upon length, but also based upon ID, and even lesser so on IATs.) -This makes the harmonic wave tuning occur at a very low RPM, but ALSO moves from picking up the 3rd harmonic wave (like a single plane or dual plane) to picking up the 2nd harmonic wave, which is much stronger and makes the wave tuning effect stronger- it's almost 3 PSI of harmonic wave tuning "Boost" with the TPI and chrysler cross-ram intakes.
The LT1 was a move in the extreme opposite direction, focusing on more airflow, 3rd wave, high RPM tuning.
I like where the LS ended up as you have a total engine combo that can spin to 7,000 RPM so you want the long-ish 3rd wave runner tuning to help that mid range torque but you don't want to choke airflow.
-I'm testing out (ok, not testing out; using it as my only intake; I'm not going back) what I think GM SHOULD HAVE made the TPI intake: 19.25" runner length from plenum to valve, 1.75" ID, 830 CFM throttle body, and a plenum that's double the volume of the GM TPI -it means you pickup the stronger 2nd harmonic wave, but up at a much higher RPM. Intake wave tuning only helps in about a +/- 500 RPM range of torque peak, though; exhaust tuning works over a 2,000 RPM range.
"Free" Extra cylinder fill is great and == extra torque at the tuned RPM; you just have to choose an intake with runners that put that extra torque where you want it and can use it.
You also see the same thing play out with some of the new LS Cross-ram intakes, too.
-If I could buy a Chrysler-style cross ram for my SBC, I would have. In addition to looking total BADASS, they're both long like a TPI-style intake AND have a way straighter air path into the cylinder. The old SBC Offey cross-rams intake just aren't in the same category of cool and runner length.
Adam
Last edited by NewbVetteGuy; 12-13-2018 at 02:08 PM.
It's not my fault you can't tune as good as GM engineers.
In the early 90's with the very low hood coming out on the 93 camaro, GM developed the Gen 2 LT1 intake:
They originally did it as an interim solution to the 93 camaro's hood clearance, but discovered it was so easy to tune they kept it and put it in production, despite the poor midrange performance compared to the TPI intake. I had this intake and engine in my 96 impala ss. We were looking for an option that would give us more torque in the midrange, as the impala was a heavy *** car, and the Lingenfelter Super Ram was too damn expensive. So we had to look for alternatives.
Back in the late 90's, Accel made an elbow that would adapt the stock Gen 2 LT1 throttle body to GM's Performance Parts carb LT1 intake...
which was a standard Edelbrock Performer RPM intake modified for the LT1:
Maybe the intake elbow acted as a spacer, but we never had a single issue with that intake after we got it tuned and it pretty much bumped our torque curve by 30-40 ft/lbs across the entire rpm band.
I couldn't find a picture of the exact setup, but here's something similar. Plus, it shows injector bungs welded into a carb intake, which is what I was suggesting to the OP in the first place:
Maybe the OP can keep his excellent midrange and still run MPFI by using a similar elbow. Edelbrock and Holley both make an adapter elbow for the LS1 throttle body.
Well please tell us more and any pictures you may have of the dual plane conversion to EFI. Myself I have one in the works for my 94 camaro w/2nd gen sbc. The more I looked into a Super Ram with it's high cost and difficult installation I began to look elsewhere. So far I acquired a converted TPI plenum instead of using a intake elbow like Nitrous Outlet sells: https://www.nitrousoutlet.com/perfor...ake-elbow.html
And I'm looking for the 2nd gen sbc LT1 dual plane to convert to multiport EFI planning to have an experience shop do the modification. So far I found only one intake specialist shop advertise the dual plane conversion but haven't approached other shop's for this yet though I'm sure others will take my money for this.
A dry runner EFI just seems to be less problematic than any wet runner though as Paul mentions there may well be hidden complications with this as good ideas and good sense can fall apart when the rubber finally hits the road. And we do stick our neck out when using modified parts as just one bad weld or one hidden leak can destroy an honest effort. But to me it's worth the effort to try as with a TPI plenum a dual plane intake takes a stockish look as sleeper intakethat could boost mid-range torque/power. As for the OP I would suggest a step up dual plane from the Performer to like the Performer RPM or or a similar Holley product.
Condor7 good luck with whatever you choose but please post your results as it helps us all - results good or bad.
Well please tell us more and any pictures you may have of the dual plane conversion to EFI. Myself I have one in the works for my 94 camaro w/2nd gen sbc. The more I looked into a Super Ram with it's high cost and difficult installation I began to look elsewhere. So far I acquired a converted TPI plenum instead of using a intake elbow like Nitrous Outlet sells: https://www.nitrousoutlet.com/perfor...ake-elbow.html
And I'm looking for the 2nd gen sbc LT1 dual plane to convert to multiport EFI planning to have an experience shop do the modification. So far I found only one intake specialist shop advertise the dual plane conversion but haven't approached other shop's for this yet though I'm sure others will take my money for this.
A dry runner EFI just seems to be less problematic than any wet runner though as Paul mentions there may well be hidden complications with this as good ideas and good sense can fall apart when the rubber finally hits the road. And we do stick our neck out when using modified parts as just one bad weld or one hidden leak can destroy an honest effort. But to me it's worth the effort to try as with a TPI plenum a dual plane intake takes a stockish look as sleeper intakethat could boost mid-range torque/power. As for the OP I would suggest a step up dual plane from the Performer to like the Performer RPM or or a similar Holley product.
Condor7 good luck with whatever you choose but please post your results as it helps us all - results good or bad.
Sorry, I don't have any pictures. This was before the days of the cloud and any hard drive I had with them is long gone. Anyway, I didn't modify the intake myself, I had a shop weld in the bungs and the fuel rail mounting points. Because of the stock wiring harness, we mounted the MAP sensor in the elbow behind the throttle body. I guess we dodged a bullet mounting it there instead of in the manifold itself, since the elbow in effect acts as a ginormous spacer. Anyway, we didn't have much trouble tuning it and while we did not see an increase in rear wheel horsepower, the midrange torque was up 30 to 40 ft lbs over stock (running a Crane cam p/n 104227 - 210/224 at .050 on a 112 LSA and 5 deg advance). The intake cut half a second off my 0-60 time and made a big difference in the feel of the car when passing on the highway.
Last edited by sstonebreaker; 12-14-2018 at 10:03 AM.
Yes I expect the dual plane to live up to it's carbureted reputation as a torque producer as it reduces the reversion both with the split plane and the intake valve timing order. And the runners are not equal length which spreads the power band instead of an peak at a single RPM. But the added turns do increase some amount of restriction/pressure loss - so the larger the runner the better here as there is no fuel yet in the air charge to drop out.
A technical problem I added myself is I want to keep it smog legal in Nevada. Since the EGR is only a visual at the inspection I can bubba an EGR on it but considering a cut and paste with welding aluminum. Using a TPI plenum will/should give it quite a stock look.
Hey this is what hot rodding is all about - having fun with modifications.
Yes I expect the dual plane to live up to it's carbureted reputation as a torque producer as it reduces the reversion both with the split plane and the intake valve timing order. And the runners are not equal length which spreads the power band instead of an peak at a single RPM. But the added turns do increase some amount of restriction/pressure loss - so the larger the runner the better here as there is no fuel yet in the air charge to drop out.
A technical problem I added myself is I want to keep it smog legal in Nevada. Since the EGR is only a visual at the inspection I can bubba an EGR on it but considering a cut and paste with welding aluminum. Using a TPI plenum will/should give it quite a stock look.
Hey this is what hot rodding is all about - having fun with modifications.
What does that have do with it - the manifold? Figuring out smog is along way off. But I would appreciate any information on using a dual plane for EFI.
You're the one that said you wanted to keep it smog compliant. I was just asking how they determined that where you live. If they use the CARB standard, one of the best guys to ask is probably this guy. He's been doing V8 conversions in Kalifornia for years. If not, your best bet would be to ask around and see which inspection stations follow the spirit of the law vs the ones that mindlessly follow the letter. In my neck of the woods, any car prior to OBD2 has to either pass the tailpipe sniff test or no test at all depending on what county you live in. If you have to pass a sniff test, you should be golden. A visual inspection on the other hand...
Smogging with that manifold is not my major concern through did want to mention I have something in the works for that. I can always resort to registering the car as a classic here in Nevada and avoid smogging the car all together. If you want to know more about the smog laws here in Nevada you can do an internet search just like I would have to do to explain them to you. And my location is in both my profile and my signature. But Nevada smog information is not what I am looking for on this thread. Converting a dual plane intake to EFI is something I am very interested in and was happy to read here someone else has used one. And I found even GMPP has a dual plane intake for the LS3 with injector casting bosses they describe as nitrous/ injector bosses which hints GM is doing some suggestive advertising with that.
I have the impression EFI converted dual planes may not be a simple modification as the runners are unequal height while the injectors need to be at the same height to fit the fuel rail correctly w/o leaks. Getting the injector to produce a good shot at the back of the intake valve may be compromised to get everything to fit up. Tuning may be more complicated with less reversion, different runner lengths the VE may have a difference between cylinders - or a spread in VE at different RPM. But none of us have laboratory to do research and development so we use plenty of assumptions to make up the difference.
OK, I guess I drew the wrong assumption from your post - I thought you were trying to pass a legal smog test. As far as the injector height on the dual plane, that's not a problem - while the openings of the ports are at different levels, they all have to enter the head at the same height, so that's not an issue. As far as tuning, it appears the key to that is to provide a space at the top of the plenum so the MAP sensor gets an accurate signal, which can be solved by adding an elbow to the top of the plenum which also allows you to use your stock throttle body (assuming you can fit it under the hood).
The TPI plenum I have is huge compared to an air elbow and a good vacuum signal should not be a problem. It has a aluminum carb spacer welded on as mount and allows use of my stock throttle body (it was previously owned/ran by a C4 corvette owner so I know it works). And if height becomes a problem I can default back to an air elbow like the Nitrous Outlet part I previously linked - a nice looking piece but doesn't have the ribs on the top like a stock TPI plenum (or LT1 intake). But I plan to sort that all out long before installation.
Oh I see, I didn't realize you were using the TPI plenum for the elbow - I thought you were going to use the whole TPI intake. I was wondering how you were going to fit it under the hood. Well, sounds like a good solution. Good luck.
Thanks everyone for a very spirited discussion. Just to clarify, my current intake for my Terminator setup is the Edelbrock 75014 Performer RPM. I chose it because it complimented the heads and cam RPM range. Notice it does have the divider cut out slightly. I also had to use a spacer under the throttle body because with the vacuum elbow installed on the intake (right on a rear runner) the terminator would not sit down and seal without hitting the elbow. So there is a spacer as well as the factory divider under the terminator. I have read several things on the manifolds. As some have suggested, the Victor single plane is an excellent choice but I am concerned that it puts the heads and cam RPM range out of wack. This car is a daily driver with some spirited driving. I am still investigating going to a MPFI ans as I mentioned, I really can not find a dual plane manifold that has MPFI injector holes. Everything i see is for single plane. I'm good with a single plane MPFI but most start in the 3000 RPM range. That was really my question. Would changing the manifold to a MPFI manifold that starts power at 3000 RPM be killing the rest of my setup? Holley's MPFI manifold, a single plane, starts it's power band at about 2000 RPM. I'm guessing that really is the MPFI manifold of choice for my setup? Holley states that their MPFI manifolds are a 2000-7000 RPM manifold and a 2500-7000 RPM manifold. I have read the Holley forum and other sites to death and have not been able to determine if using a MPFI manifold with an RPM range different than what my current cam and heads are will be okay or will just rob everything from the motor. The FAST MPFI manifold has a 3000-7500 RPM MPFI manifold. I think that is way too much, even if it is only air flow to the heads. The Terminator works great in the current setup. No idle concerns, lots of power, fuel economy is decent. I did change the TB to progressive rather than leave it as tandem after doing more research. Definitely more user friendly. I like to mess with my motor and would like to see if a MPFI system set up correctly will be even better all around than my current setup. Again thanks for the spirited discussion. Any help or thoughts would be appreciated. (Before it is said, I don't want an LS motor, well not yet anyway).
Below is the Edlebrock MPFI manifold that looks like an air gap. 2000-7000 RPM range.
the Holley 300-260 is the one I am considering for my motor. (2500-7500) It also has a smaller height which is important as well because of hood clearance. Below picture. The Holley above is slightly different, like an air gap. More $ as well.
Going from a large intake port outlet to a small head intake port IS a problem you want to avoid. -You either want to gasket match the head to the intake, or get an intake with a port that takes the same gasket as your heads. (If I remember right DART has an "SHP" branded dual and single plane intake that should be a perfect match for those heads..)
12-13-2018, 01:43 PM
