so i was reading a thread on here the other day that referred me to a GM high tech link that talked about the guys over at Livernois motorsports doing some cam swaps and dyno runs on the ls2, the baseline numbers on the motor seemed par and then they swapped to what seemed to be a somewhat mild cam 218\220 570lift 114lsa and got 90hp out of it?! how can this be? i must be missing something here

 

this is the thread http://forums.corvetteforum.com/show....php?t=1497046

 

Yeah that does seem a little optimistic of them but it's got to be for real I'd assume.
Keep in mind that that was through headers and likely no real exhaust nor cats restrictions and I'm sure tuning was done for each cam swap as well.
They say they first baselined the stock LS2 (iron block not aluminum but C6 specs otherwise) at 400+hp (crank) but I wonder if that included the headers and tune as well.

 

I read this article completely through, and see a bunch of gaping holes in the narrative and the numbers. I suspect that something was lost in the translation between Mr. Millen and the writer.

These dyno pulls were done on a WinPep Superflow engine dyno, not a chassis dyno. So first you need to adjust all the numbers down by 15% or so. For example, the article quoted 402 HP for the stock engine, while my C6 A6 dynoed at 339 HP on a Mustang chassis dyno. Also, the engine was an iron block, not the C6 aluminum block engine.

The cam results look very fishy to me. First, I have yet to see anyone report a 90 HP (OK, 75 HP less the 15%) gain from any cam only mod, let alone from a very small 218 cam. There is nothing special about the grind that would account for this kind of power gain. Next, look at the comparison to the much larger Stage 2 cam, which gained only 4.8 HP at the same peak of 6400 RPMs. Yet TQ actually DROPPED, and occurred at 5K RPMS, 200 RPMs lower. I have never seen this kind of result from increasing duration by 15 degrees, and lift by .3".

There are other strange inconsistencies. In the discussion of the merits of the 110-112 LSA vs. the 114, it states that the 110-112 LSA would produce 10-15 more HP from 2K to 4500 RPMs, be equal up to 6400 RPMs, then would carry the HP curve before falling off. In other words, it would be much better or at least equal to the 114 LSA. So why do they offer the 114 LSA for every one of their cams? The answer is that the article got the argument garbled.

Same thing applies to the discussion of the stock computer "pulling timing", and whether they left 10-15 HP on the table by not using any "tuning magic". Immediately thereafter it says that "Dan did tune the engine to correct for the computer pulling timing". Can't have it both ways.

I have seen this article cited by others on this forum (read Zig), getting it confused with the timing pulled by TM. IMHO, the basic description of what is going on is just flat wrong, or at best misleading. The computer doesn't sense increased airflow and decreased exhaust backpressure to adjust timing, it senses (computes) A/F mix. When the engine starts to run lean, it then adds fuel and reduces timing. If the lean condition also causes the cats to heat up, the overtemp condition can also cause timing to be further reduced.

So, bottom line is don't take this article as Gospel. Livernois has a good reputation and I'm sure they make good products. But I won't believe these HP claims until I see them duplicated by forum users, and validated on a SAE calibrated chassis dyno. I have some experience with a similar grind, a 218/224 .550" 114 grind that I installed on my '99 Camaro SS. I picked up 23 HP, going from 360 (boltons only, shorty headers & OEM cats) to 383 HP/TQ. This was after a dyno tune by one of LS1Tech's Moderators. If I had gotten 75 HP from this cam I would have taken out a full page ad in GMHP! Not so......

 

There are some inaccuracies and as often is the case with magazine tests the numbers may be on the optomistic side. But there have been a couple of similar tests on the LS1 that haven't been too far off this either, and experience says it isn't all hooey.

So don't count on 90 HP from just a cam swap, but two things that are consistent are: (1) the LS2 can benefit a lot from a cam, and (2) a fairly mild cam will make almost as much gain as a monster unless you really work over the rest of the engine.

Hey, even if you deduct a bit for magazine hype and allow for ideal conditions a gain of 50 RWHP isn't unrealistic for a cam like the XR265. Remember that the '02 Z06 picked up 20 HP from (mainly) a .025" increase in lift.

 

why wouldn't this be true ?

doesn't increased duration result in the valves being opened longer.

how is torque built ? isn't it a result of a closed enviroment ??

"...Duration has a dramatic effect on the idle quality and rpm range of the engine. In general, longer-duration cams will raise the rpm at which peak torque will occur, and raise peak horsepower. The drawbacks are losses in low-rpm cylinder pressure, torque, and idle quality. Therein lies the tradeoff in cam selection: go bigger for more bite up top, but too big and the engine will become increasingly hard to live with. ..."

http://www.corvettefever.com/techart...ofile_testing/


i got the impression that they were telling us they didn't do anything more than adjust the timing for the combination.

i simply proposed an idea as a possible explaination to the tm feeling some have experienced. show me where i am wrong and i'll agree with you.

ok, how then does it calculate the a/f ratio ?

agreed, try to learn the concepts and evaluate if they will apply to your sitiuation.

but, aren't they a 'tuner' shop that folks claim know their stuff. now it appears you are saying, "don't believe the tuners, show me". isn't that along the same lines as my questions related to tm.

not trying to get the debate going over here. just providing my comments since i was referenced.

 

You're debating with yourself again.....

 

what i got from the article was they didn't tune the engine when they did their baseline run. then after they put their cam in is when they tuned it. i'm no genius with reading comprehension but you might want to read the article again the whole way threw.