the convertor and 4.11 gears will eat up some rwhp. i'm pretty sure that GM used the F.A.S.T engine management system when the got the advertised 420hp for the hotcam kit. somebody correct me if i'm wrong.

michael

 

I'd be happy with those numbers! Considering your using stock LT4 heads with a mild cam through an auto with 4.10 gears. Don't know how much your car weighs, but providing you have traction 12 sec time slips are yours.

Enjoy!

 

So even though I am tuned for 30# injectors I should go smaller?

 

I am not a tuning expert by any stretch but if you are properly programmed for 30#'s then you should be fine. The computer handles the amount of flow anyway, automatically. All that I was saying is that the stock ones can handle the amount of hp that you guys and myself are putting down. The $200 and time could have been spent on somthing else. I don't think you would actually see any gains on a dyno just changing injectors.

 

ur2slow...have you checked your injector duty cycles? My car only traps slightly higher than yours and w/ 24#'s, the duty cycles were up at 98-100%. I knew I wouldn't gain any power w/ the 30#'s, but it's definitly safer running them at 85% and under duty cycles so you can rest assure one is not going to lock up under full throttle.

 

Your method of calculation is giving you false FWHP numbers. When converting from RWHP to FWHP (a 'percentage of' to a 'whole part') you need to DIVIDE, not multiply. So, considering a drivetrain loss of roughly 18% for an A4, that means that your flywheel HP is roughly 421.46 (345.6 / .82). That's really good bud, I would be very happy!!

 

My car was done at Speed Inc. and Jim and Larry know what they doing. I have 24# injectors still, but making a little more power

Good numbers man

 

Sorry, could you explain this in a little more detail as to the(a 'percentage of' to a 'whole part')you need to DIVIDE, not multiply. I guess my HP is right about what GM is claiming then. I am trying to get to the track this week to see what ET's I can run on BFG drag radials.

 

No problem bud, it's real easy to do it the wrong way. Let's see if I can explain it...

Let's say that a V8 motor strapped to an engine dyno pulled 300hp (fwhp). Now let's say that that engine was bolted into a car with an automatic transmission and strapped to a vehicle dyno. What's the estimated RWHP?

Condering that most A4 setups eat approximately 18% of the engine's output (to turn the tranny, drive-shaft, and rear-end) then the approximate RWHP in this case could be calculated by simply asking "What is 82% of 300?":

300 * .82 = ??? [answer = 255]

Cool, 255rwhp for that setup. Okay, but what if you only had the RWHP number (percentage of an unknown 'whole') and wanted to find FWHP (the unknown 'whole')? The approximate FWHP can be found by reversing the above formula (divide each side of the equation by .82) to ask "255 is 82% of what number?":

??? = 255 / .82 [answer = 300]

Note that the INCORRECT question would've been "255 is 118% of what number?". That would give a lower number because 18% of 255 is not equal to 18% of 300; or ".18 * 255 < .18 * 300". Make sense?

So, in summary:

whole * percentage = percentage_of_whole

percentage_of_whole / percentage = whole

Just remember that the engine is the source of all this power, so the engine's FWHP is always the "whole".

Hope this helps!

 

Does anyone have any real evidence that it was GM who claimed "420-430HP"?

I believe it is Pace Parts and Summit that are making the "up to 425HP" claim. And I believe they are basing that on the MORE Performance engine dyno test of the LT4 conversion. MORE got 429flywheelHP. The test was printed in on of the Chevy mag's about 3 years ago, and reprinted about 6 month ago in "Pontiac Enthusiast" or some such magazine. MORE failed to indicate in the article that you also need LT's, the larger TB, and few other things. MORE also failed to mention that they used a $4,000+ MoTeC engine management computer for tuning.... and that unit has a few capabilites that the stock PCM does not have.

 

yes, back in a article out of a magazine on the LT4 heads and"hotcam". on a engine dyno through longtubes with speed pro engine management it made 420hp

Its an old article, i think from 92 or 93'

 

Couldn't be older than 1996.... since the LT4 didn't exist before then.

 

I will say those are probably typical or average power numbers for the LT4 conversion, but you could have gotten quite a bit more power by doing a little more research and for the same and maybe a tad less $$.

My mods:
Stock heads ported by Lloyd with 2.00/1.56 valves
XE 224/230 cam, 114LSA, 110ICL
1.6 non-self aligning rockers, guideplates, hardened pushrods
Cmotorsports "618" valvesprings
LT4 extreme duty timing chain
FLP longtubes, cutout
BBK 58mm TB

Vig 2800 converter
3.23 gears

I put down 362 to the wheels two weeks ago. That was with 13.6 air/fuel ratio. At 12.8-13.1 AFR I think it would have put down 370 (why I didn't reflash 1 more time to see I don't know). Divide by .82 and I am making roughly 440hp at the flywheel and if it does make 370 next time I dyno that's equivalent to 450 flywheel.

Due to the fact both of our cars are A4's with converters I think the numbers are similar and comparable. Your converter probably eats up a few more hp but mine was a tad lean so I think that's a wash. I know the Hooker LTs are good for 3-5 more HP than the FLPs too.

Nothing wrong with the LT4 heads..there's plenty there to port in the future and ported they will far outflow a set of ported LT1s, so that is a good investment in a way. But I am just not a big fan of the hotcam. First of all everybody has it but more importantly its sort of a old design and there are lobes out there that are far more advanced (like the Comp XE series).

So I guess my point is that its a fine combo and you're making decent power but with a little more research you might have been able to save money and make more power at the same time.

 

dont let that dude confuse you with all those equations. you did it right the first time when you got 406 or whatever, you just used 15% instead of the 18% for an automatic.

 

Ok Mr. Smartie, figure this out. Let's stick with the 406 number he mentioned. If 406 is right, then why doesn't that number times 82% equal his dyno values of 345 instead of 332?

406 * .82 = 332.92 (This doesn't match his dyno)

421.46 * .82 = 345.59 (This does)

Go back up and read my post to clear your confusion, dude. It's right!