RPD Vs. Dyno
 

Anyone have RPD and compare numbers to dyno with bolt ons and tune? I have well, everything you see in my signature... bolt ons and trifecta tune. My car's RPD has said highest for both Hp and TQ are around 325 ea. That doesn't seem quite right for Crank HP and TQ. The tune gave me about 22 psi (spike). I've had a re-tune done, but it actually hindered performance a bit. I figured 320's or so should be numbers to the wheels, not to the crank (which is what I would figure the RPD to read). I haven't had a dyno yet, but I'll be tempted if I can ever get these numbers up a bit. I'm waiting on a new tune to come in, hopefully I see something different. My guesstimates based on what GMS1 advertises, are that my bolt ons and aftermarket tune should get me (obviously the reason to go aftermarket is to see bigger gains than GMS1) somewhere in the mid three-hundreds or so for Crank TQ and low three-hundreds for crank HP. That's not unrealistic is it?? Just trying to get a feel for what other people are seeing. Thanks for any inputs...

i think theres too many variables. Now i know that my car pulls significantly harder when its 50's outside. On those days im seeing 325hp, and 328lbft. Last week in the 80s i saw 325 and 320lbft. my only mod is airfilter and trifecta 21psi. I should throw on my superchips to see where it reads out.

I get that, for sure. The difference in those numbers is not much at all. I would be ok if my numbers were a little better and varied only due to the temp. I guess I should find some people with the same mods and tune who have done the dyno to see what they're getting.

Orrrrr, I know this is crazy talk and all, you could just book some dyno time to get real world numbers to compare. It's really not very expensive to get some simple dyno pulls done

I think I probably will after the new tune comes in. I'm a cheap ass though, but If I see some improvement in the numbers with the new tune then I'll dyno to compare. Either way, I'm pretty happy so far with the power I feel in the car. Love the 'select a tune' feature from Trifecta!

Bump

RPD is innacurate. Said I had 310TQ at the crank, but when I dyno'd I had 365.

That is the first time I have heard that. Thanks for the response!

with the superchips tune it was pretty on. After that, not so much. Mine read 310WHP/340FtLbs, I put down 324WHP/404Ftlbs.

Hmm... well, new tune coming in, guess I have to dyno. I will post results when I get that done.

Mine has never shown over 230hp or 240 tq GMS1 and 5100kms I only use mine as a heads up display for the speedometer at least thats accurate (confirmed with gps) more so than the slow responding dash unit, I also use the intake air temperature and fuel pressure display the rest seems like a giant waste to me, woud have been better to cut out the rpd and put in GMS1 from factory for the same cost!!

I like to RPD, mostly its concept. Could have been done a little better, but once again we come back to cost and value. What you get for the cost in a compact GM sports coupe, it has a good amount of value. Obviously we're seeing from this forum that the HP and TQ readings are inaccurate. Hopefully the other readings aren't off by much. I would venture to say that the nature of determining crank hp and tq through a dash gauge is a bit of a stretch or I'm sure a lot of cars would have introduced the feature a long time ago. Learning a lot from the responses, thanks guys!

I use the RPD for the digital speedometer, lateral acceleration, bar graph/EV meter for the tachometer, and the gear indicator. I don't use the analog speedometer anymore.

I definitely used the digital speedometer as the only gauge when I first got it, now I watch the turbo a lot and generally don't care how fast I'm going lol... jk, but no seriously..

Pretty sure the rpd shows crank not wheel power.

Correct.

It is also no longer accurate once tuned.

yeah I know, typographical error on my part. What it really shows is air moving and some formula to deliver a "HP Estimate."

When I tuned with the superchips cortex though, it was dead on WHP levels. I think once you start moving 300+ whp levels of air, is when it becomes innacurate.

I expected that it would only read crank power... didn't realize it wouldn't read with mods. Makes me wonder what else might not be accuate on there....

I think it only has tables for stock timing

It shows my 20* of timing on the advance table nicely when I got WOT

The HP/Torque page is the only one that is inaccurate and that is really because of the ECU, not the RPD. The RPD only shows was the ECU is broadcasting. Any other scan gauge would show the same incorrect things for HP/torque.

All other pages are accurate.

Even with the GM Stage 1 upgrade, the RPD will not display the correct numbers for the HP/TQ page?

I believe GMS1 is the exception. When I say tuned, I meant aftermarket tune.

What I mean is it can read it but doesnt know how to relate it into hp/tq numbers. So at 30lbs/min its probly showing what the results would be for 10*(whatever stock is) of timing

That's very possible. The HP/torque numbers are obviously calculated somehow, so that could be a part of the calculation the ECU uses.