I know this isn’t truly internal engine related, but in the interest of having one thread to discuss these results we are posting them here.
Intake Test: LS2 vs LS6 vs FAST
We here at GearChatter are committed to providing real answers to the questions everyone is asking when it comes to engine components and the ability to make horsepower. Intake manifolds have been a hot topic, so we had some independent testing done by a professional engine/dyno facility to find some answers! Read’em and discuss — there is more to come!
Engine Description: GM Performance 5.7L LS1 crate engine tested with Kooks F-body 1-3/4” long tube headers with 2-1/2” lead pipes into Flowmaster mufflers. Factory front drive accessory was used with the water pump, power steering, and alternator. Stock LS1 heads and short block, GM Performance “Hot Cam” with LS6 valve springs are the only engine upgrades.
Engine was tested using the factory PCM. The intent was to test the intakes just as the average user would install them — no custom programming. Granted, custom programming would increase the power of each combination somewhat, as the detailed info from the tests indicates that each intake had some “holes” in specific RPM ranges that could be corrected to improve the HP of each intake. But in the end, the general tendencies would remain as they are. We have over 30-pages of test info for those who want to dig-in to the detailed data and we would be more than happy to mail this info to anyone who wants to see it for the price of the copies plus postage.
We have summarized the test for your viewing pleasure.
Some points to keep in mind; we have included averages for specific RPM ranges – Low, Mid, and High. The engine does not stay at a constant RPM, so we feel it is important to see these numbers. Hey, if you leave the starting line at 4500 and shift at 6300, then it might be nice to see the average for that range!
Do not forget, this is a 5.7L with a rather mild cam upgrade! Engines with different RPM ranges and more cubic inches may have totally different results. We are just reporting what we tested. And BTW, we will have some intake results for a 6.0L LS2 very soon!
Test 1 – LS6 Intake with Stock 78mm TB.
The best low and mid range numbers of all the combinations. The LS6 would seem to be the best bet for all-around street driving/racing on this combination. As the engine moves past the 6000 rpm range, the LS6 plenum volume may not be large enough to keep up with the demand for more air. The LS6 made the highest peak torque number.
Test 2 – LS2 Intake with Stock 78mm TB.
We made a thin adapter to bolt the 78mm TB onto the LS2 intake to see the real comparison from LS6 to LS2.
Want to kill 10hp and 10ft-lbs of torque? That is what happened! Obviously the 5.7L does not like this big intake. We thought the 78mm TB might help by keeping the air velocity up on this big plenum intake. Did not work!
Test 3 – LS2 Intake with FAST 90mm TB.
As long as we were here, let’s try it!
Our intuition told us that this probably would not work and it didn’t! But it is interesting to note that the power was not significantly hurt from the addition of a bigger TB either. In fact the two curves are almost identical.
Test 4 –FAST with the FAST 90mm TB.
Now it is obvious that the FAST wants to make more power up high — above 6000rpm. But when you look at the low and mid range the LS6 is definitely better, but when you hit 4000rpm the FAST wants to carry the torque curve further than the LS6. The FAST made the highest peak HP number, 432hp @ 6000rpm.
Lots to discuss here; plenum volumes, runner lengths, TB sizes, what would ported heads do, etc. We have heard of people bolting on the LS2 intake to a 5.7L and the car felt lazy, it is easy to see why! The engine lost torque everywhere!
