How much RWHP do GEARS steal on the dyno?
 

Alright, so I had the chance to get a dyno in today for cheap, only 1 pull.. I was with a bunch of friends and said oh what the hell. I'm comparing the results to my previous dyno of 270.7 RWHP and 306.6 RWTQ. I'm not going to say what the new numbers are just yet.. I want to see people who have dynoed without and then with rearend gears. I'm trying to figure out how much it hurt me. Between the previous run and this run I added Steeda U/D pulleys and the FRPP 4.10 gears. Both dynos were dynojet's.. but the one from today used the tail pipe sniffers.. which I'm also curious if they give a very accurate a/f ratio reading, because from my previous dyno my A/F was right on.. and now its a little bit lean. So.. anybody dynoed without and with rearend gears?

I havent yet, but I heard that with gears you do tend to dyno lower then without gears.

yeah.. that's what I heard, just trying to figure out how much lower because I think the dyno I went to is JACKED UP.

How about this... after my car was tuned last time at 2500 rpms I was at about 12.5.. this new dyno says at 2500 rpms im at 15.5.. all i did was add u/d pulleys and gears.. how the hell does that effect a/f? i don't get it i guess.. im more lean than before i got tuned after adding full exhaust and tb, plenum, cai.. wtf

im just guessing but i wouldnt think gears affect the numbers on the dyno. you still do the pull in 1:1 drive right?

no.. I've always heard they take away hp on the dyno.. it has something to do with it accelerating too quickly for the power to build and the dyno to log or something weird like that

On a dynoJet with 4.10's...your nott gonna see the same numbers u had before the gears. But you shouldnt loose to much HP on there also...im guessing about 7RWHP
Just remember that the HP is still THERE...but the dyno cannot read it like before due to the greater toque from the wheels spiining faster..

And about the your new air/fuel readings.....now thats just fu**ed up...maybe his o2 readers was off? is this the same place you originally went to? u may need a new tune..:bash:

hmmmmmmmmm learn somthing new everyday. thanks

no this isn't the same place I orginally went too, the other place is the ones who made my tune. the a/f wasn't way off.. at 2500 rpms it was at 15.5 though.. when it was tuned it was at 12.8 :shrug: and all the way through it's just a little lean when before it was dead on. someone told me (import guy) that the rearend gears cause the engine less drag so it will run a little bit leaner, kinda makes sense to me.. what do you think?

ya that also makes sense to me....



can u post the graph..?

the before and after graphs?

If your pull was made with the car cool, the A/F is not going to be the same as when warmed up. Those guys in Evansville are a joke BTW:bash:




Jay

thats true...lol

Was your car at full operating temp when dynoed??????????

My tuner made sure my operating temp was at normal before tweaking the Air/fuel and tuning it.

Jays is right

csledd... stop listening to ricers. That's almost a ludicrous statement to make.

HP is a measure of WORK COMPLETED OVER TIME. How much crap did you move from here to there in how long. TQ is a measure of actual force.

Using hotter gears like 4.10's over a 3.27 will yeild almost no change in HP levels but you should see a multiplication of torque by a tad. I would expect your total TQ rating to climb by a bit but your HP should be within a few percent of your last dyno. You can discount the pullies for any power below 3500rpm. Even if you use 5.30 gears your engine will only move so much air in a given amount of time and that directly predicts your HP. The wheels will turn more violently when power is added because you've multiplied the tq by 5.3 instead of 4.1 or 3.27.

Everyone clear? Go read a math book if you're not.

I don't know what is true and whats not. What I do know is that I and my tuner are going to do some experimenting this summer.

1.) Testing a BBK fenderwall CAI, K&N filter only, JLT RAI.
2.) U/D pulley's
3.) and finally the before and after when I install my 4.10s we'll see if there is a difference.

You will lose hp on a dyno with a lower gear. I lost 10 hp switching to 4.30's from 3.73's. I cannot explain why you lose I just know you do. I had this talk with Ken at MD motorsports when I dyno'd. At any rate it doesn't really matter what a dyno sheet says it's what those little slips they give at the shack on the return road say.

Came across this on another forum and I thought of you guys! lol


"The 4:10 gear will show less horsepower than the 3:27. The reason is
due to rate of acceleration changes. The rate of acceleration is quicker
with the 4:10 because of torque multiplication being increased to the
rear wheel. The horsepower will show less because the targeted RPM is
met before the horsepower has a chance to overcome the rotational mass
(dyno, drive line, etc.) or moment of inertia in speed. Because the
speed is decreased and the RPM is met faster, the horsepower never has a
chance to catch up with itself, so to speak. The overall ratio of 1:1
will always produce the most horsepower on the chassis dyno. Having said
this, a similar problem can occur with horsepower loss when the rear
gear is too high. The horsepower is being absorbed in just trying to
keep the rotational mass spinning. Please keep in mind that your
engine's horsepower never changes but what gets to the dyno or drive
surface does."

well I seriously think those numbers are bogus.. my car was definately NOT anywhere NEAR full operating temp.. this is how it seems teh dyno operator proceeded..

turn car on after sitting for about 3 hours, roll to about 2500 rpms and shift to 2nd, roll to maybe about 2000 rpms in 2nd shift to 3rd, roll to about 2500 rpms and shift to 4th, roll to about 2700 rpms let off for a few seconds and then get on it as hard as possible!

yeah.. wtf.

ive never heard of a 4th gear pull....its usually in 3rd gear for its the most balanced or average gearign

you sure? I thought on our cars they're usually done in forth

My auto was done in third I believe so the manual to me would make sense in fourth

:dots:


Thanks
Shawn

lmao!:beerchug:

Please explain why the car wasn't brought up to operating temp before being hammered on the dyno. :loser:



Jay

Or listen to the people with the experience who have CONSISTANTLY seen a loss of about 10 rwhp from going from stock to 4.10's. Calling the people with the experience ricers...nice:loser:

Hey captian negative... why don't you read the post I was referencing before you go getting snippy. jagoff.

I also said you will see ALMOST NO CHANGE. 10hp is almost no change. Considering theres usually 200 and change more where that came from.

Sorry Kemosabee, me no read. My bad.