Intake manifold comparison - EFI on a mild 455

[DynoLee]

I mentioned on my other thread, that I recently performed an intake test.  I compared 5 different intake manifolds on my 455, with FAST XFI Sportsman throttle body EFI and ignition control.

I've seen many people make statements such as "you need to use a blah-blah intake with efi" without ANY support for their claims.  They have theories and opinions, but no hard evidence.  I had my own theories, and had done a little testing, but wanted to take things a bit further.

I already had an Edelbrock Performer.  A friend let me borrow a Holley Street Dominator.  I then bought a Torker II, and Tomahawk, and an old square-bore Edelbrock P4B intake.

ALL intakes are box-stock, except for having the water crossovers removed to speed up change-outs during the testing.  I would have loved to have tested a factory intake, except that I do not have one that has been modified to accept my square bore throttle body and I don't want to mess with adapters.

To be clear, the Performer and P4B are both dual plane designs, and the other 3 are single plane.

My good friend and professional EFI tuner, Eber Saenz, sat in for the testing and helped me optimize the initial tune.  We optimized the tune for the Performer intake (which was already on the car).  Once we felt that we had all the peak power that intake would provide, we started testing the other intakes.

Each dyno pull was data-logged with the FAST XFI software.  The program had sufficient capability to keep the AFR close to target at peak RWHP for all of the intakes, but all of the intakes could have been fine-tuned to provide smoother power at lower RPM, but none were likely to perform substantially better than what was seen in the testing.  Due to time constraints, I only had time to make one pull with each intake, so no further tuning was attempted - and we left the tune unchanged to make the testing as fair as possible.  Note that even though the tune was optimized for the Performer intake, ALL the other intakes made more peak HP, even though they were using the same tune!

So here is the first results graph to consider:

[DynoLee]

Now, a quick lesson on presenting data. 

Notice that the graph above shows power output starting at "0".  Presented in this manner, the intakes all appear to perform amazingly close to each other, and that is an accurate conclusion.  Few people can truly "feel" the difference in performance between these intakes in real world driving, and I doubt the difference at a drag strip would be more than maybe 2 tenths at most between the best and worst intakes.

Now, I will zoom in on the results.  If you have the DynoJet software (it is free to download) and have the dyno data (take a USB memory stick with you), you can also manipulate the graphs as you wish.  This graph focuses on the actual range of power, eliminates the areas of no interest, and the result is sort of a magnification of the tests.



I find it interesting that the Performer was RIGHT with the P4B until about 4000rpm, then basically went flat.  Then, around the 43-4400 range the single planes finally caught up with the P4B - but just a slight bit more HP.

But, since Pontiacs typically make more TQ than HP, looking at the TQ graphs can show a bit more.  Zooming in to focus on the power band makes this even more dramatic looking.



Looking at these graphs, which magnify the differences, the Performer looks like a HORRIBLE intake.  But if you look again at the first graph, which starts at "0", then it is easier to see that the differences are not really THAT significant.

Anyway, I'm now using the P4B on my motor, and it also makes the shaker fit MUCH better than it did with the Performer.

[DynoLee]

I do plan on going back to the dyno in the near future, and seeing if I can squeeze a bit more power out of the P4B.  I don't really expect to get more peak HP, but do think that I can improve the power below 4,000rpm with more tuning & testing.  I also plan on some track testing as well, to verify the dyno results.

Oh, as for which intake design is best for throttle body EFI - I think it is pretty much a draw!  On my motor, dual planes performed best for power below 4,000, and single planes made a bit more peak HP.  I've now driven the car around with the Performer, the P4B, the Street Dominator, and the Torker II, and really could not "feel" any difference under normal driving.

Thanks to Stephen "Sugardog" Lawrence for the loan of the Street Dominator, and to Eber Saenz for the assistance with the EFI tuning.

[roadking77]

Thanks for taking the time to do this service. Very interesting. I would be curious to see how a stock intake compares. I have read and been told that performance wise theres not much diff. The advantage being a weight reduction using aftermarket.

[DynoLee]

Thanks for taking the time to do this service. Very interesting. I would be curious to see how a stock intake compares. I have read and been told that performance wise theres not much diff. The advantage being a weight reduction using aftermarket.

You are welcome!  I've been trying to put this test together for quite awhile, but a variety of things have caused delay after delay.   

I know some people have modified stock intakes to accept square bore carbs/throttle bodies, but I do not have access to one.  If anyone has one that I can borrow, I'll gladly test it!  I suspect it will perform VERY similarly to the P4B, but that is just speculation until the test is actually done.  I've seen poor results with square-to-spread adapters with carburetors over the years, so I am not even considering that option.

[DynoLee]

Here is a group photo of the tested manifolds



And for anyone curious, here is a shot of the engine bay with the Tomahawk intake installed

[tajoe]

Good picture of the intakes in the above photo. 2 dual planes, and the rest single planes. Could some-one post which intakes are what, say clockwise, from top left? Thanks.

[DynoLee]

Thank you.

From front row, left side:  Torker II, P4B, Performer; back row L to R:  Tomahawk, Street Dominator.

[tajoe]

Thanks for the identification. I'll take the 2 spread bore intakes. Then I can use a QJ.

[NOT A TA]

Great test! Thanks for sharing the results!

[pancho400cid]

Well....

This is an awesome discussion.  I see it as sorta validating conventional wisdom as far as single vs. dual planes.

Would you say that EFI improves the drivability of a single plane intake?

The post almost reads like a Hotrod Magazine article.  Thanks for the effort to write it all up!
 

[5th T/A]

DynoLee,

Thanks for taking the time and effort to post this valuable information. Since these intakes were used on a TA, did you use the factory air cleaner and shaker? Did any manifolds fit better than others? Were any better in regards to throttle and kickdown cable connections?

You were referring to the regular Edelbrock Performer and not the Performer RPM is that correct? From what I have read the performer does not flow as well as a Pontiac factory manifold. The Performer RPM is supposed to flow much better but sits 1.25" higher. I have heard the stock Pontiac cast iron manifolds perform very well, but have not seen any dyno comparisons.

Thanks again and great job documenting!

[DynoLee]

Thanks for taking the time and effort to post this valuable information. Since these intakes were used on a TA, did you use the factory air cleaner and shaker? Did any manifolds fit better than others? Were any better in regards to throttle and kickdown cable connections?

You were referring to the regular Edelbrock Performer and not the Performer RPM is that correct? From what I have read the performer does not flow as well as a Pontiac factory manifold. The Performer RPM is supposed to flow much better but sits 1.25" higher. I have heard the stock Pontiac cast iron manifolds perform very well, but have not seen any dyno comparisons.

Thanks again and great job documenting!

For ease of testing, I left the shaker and aircleaner/filter totally OFF for the testing - good question!

I have a throttle/kickdown assembly that attaches via the driver's side rear carb mounting stud.  That made it quick and easy to set up the throttle linkage for each intake.

It is the 2156 "regular" Performer intake that I tested.  I may test an RPM at a later date, but can't promise that will happen anytime soon.

I am currently running the P4B intake, and it fits GREAT with the shaker scoop.  Actually a bit lower than the Performer.

Back in the early 1990's, I had a daily-driver 79 Trans Am, automatic, 2.73 gears, Qjet, and a mild 455 Pontiac.  I raced it rather often, and with an iron pre-EGR factory intake it ran a best of 13.27 - usually ran 13.3-.5 depending upon weather conditions.  I later swapped on a regular Performer (a 2156, like the one used in my recent testing).  I made at least another 100 passes with that intake.  Best run with the Performer was 13.32 or .33 - basically about half of a tenth of a second slower than the factory intake.  IMHO, the Performer is MUCH better than what the "internet experts" state with such authority, and the P4B is even better.  The way such "knowledge" is transferred sort of reminds me of the "human centipede" movie.

[DynoLee]

Well....

This is an awesome discussion.  I see it as sorta validating conventional wisdom as far as single vs. dual planes.

Would you say that EFI improves the drivability of a single plane intake?

The post almost reads like a Hotrod Magazine article.  Thanks for the effort to write it all up!

Beyond a doubt, the single plane intakes made the most HP and the dual planes made the most torque!  But looking at the data presented on the first graph, the differences were MUCH smaller than I expected.

That said, I believe that you are correct - the EFI improves the drivability of the single plane intakes.  Carburetors rely on a vacuum signal to properly meter the amount of gasoline entering the intake, and single planes tend to NOT do a good job at that task when operating under light throttle and lower RPM conditions.  In contrast, the EFI computer is analyzing a variety of sensors and can control the fuel in such conditions more effectively.  Since my system is controlling fuel AND spark, it makes it all work even more smoothly.



To all who've offered thanks & compliments - you are very welcome, and I'm glad you found value in my testing.

[djustice]

Thank you for doing this, much appreciated!

[chief poncho]

Great thread.  Thanks for the information.  For reference, can you provide a little more detail on your engine specs? 

Bore, stroke, cam specs, headers/exhaust manifolds, exhaust system, heads (and any port work).  It's my understanding that if there are other limiting factors in an engine, the intake won't make much difference, but that a single plane really works best with a bigger cam and more air flow.  I ran a street dominator on a mopar 383 back in the day, and it was a big difference, especially over 4500 RPM over the stock dual plane manifold.  Granted that was a pretty high revving 383 not a poncho 455.

[DynoLee]

DJ & MP, thanks!  Glad to know people are still finding this and getting value from it.

Great thread.  Thanks for the information.  For reference, can you provide a little more detail on your engine specs? 

Bore, stroke, cam specs, headers/exhaust manifolds, exhaust system, heads (and any port work). 

I had another thread with more of that info.  Here is a link to it, and I believe it will answer most/all of your questions: 
http://transamcountry.com/community/index.php?topic=83904.msg5978#msg5978

This is an ongoing project.  Some of it has taken much longer than I had wanted, but life gets in the way at times    I hope to get some track times VERY soon, as well, to validate the dyno numbers.  I've dyno'ed and raced enough cars to have a good idea of what it SHOULD do, but that is just speculation until it is actually done.

More changes & testing coming next year