flamve

My friend took my rx7 to a local car meet with a dyno and this is what happened. The hp seems fine but the torque seems really low. it definitely doesn't feel like a car with 58 lbs ft of torque

RX200013B

does look low, but also nice and very flat curve! not bad on the hp! good job

NI_Racing

iTrader: (4)

HP looks right, but the torque reading is wrong. The car shouldve been near 110-120ft pounds. I think the shop may have had a sensor issue? Not sure.... but your torque shouldve been atleast double what it read....

flamve

Since I wasn't there I don't know how they hooked it up, but when my friend came back with these numbers it didn't make any sense.

I was going to use these numbers as a baseline for the rebuild I was planning, but since I didn't plan on doing anything too performance oriented, I will just run it as it is and have it professionally done this winter.

arghx

iTrader: (3)

Something's off with the torque reading.

flamve

As it turns out he also took a video of the dyno run. I did not realize it was a portable one, I thought it was at someone's shop.

http://www.youtube.com/watch?v=73q7TMq6mis

Thanks for everyone reassurance about those torque numbers, my 2 other cars have big 6 cylinder engines that are known to produce more torque than HP, and I have never felt that much less out the RX7.

PS - I know I have to clean my rims

junito1

Maybe the dyno technician is just garbage or something is wrong with their equipment or software.

RotaryRocket88

iTrader: (7)

Yes, the torque numbers are flat out wrong. The relationship between torque and HP is very simple. HP = (Torque * RPM) / 5252. http://www.dragtimes.com/horsepower-...conversion.php

If you convert the x-axis mph numbers to RPM, you can calculate torque.

Assuming a 4.1 rear end, 1:1 4th gear ratio and stock tire sizes:
RPM = MPH * 56.2

So the graph ends at 6800 RPM (121 mph), 144 rwhp & 111 ft. lbs. rwtq
At 4000 RPM (71 mph), it's also making 111 ft. lbs. rwtq
And it looks like peak torque is made at 5350 RPM (95 mph), which ends up at 122 ft. lbs. rwtq.

144 whp & 122 ft. lbs. rwtq. Not bad for an N/A.

flamve

Thanks for the in-depth explanation. I asked my friend if he had any doubts about the guy that was setting up the dyno, for starters he couldn't open my hood lol, and repeatedly asked about very odd things about the car. After getting some funny numbers from the first run, he formatted the output into the MPH graph instead of the conventional RPM graph. My friend also mentioned that no one at the car meet had any idea what a rotary was, and had to constantly explain it to them. Since mine is fully striped down you get a really good look at how compact the engine is, and that too boggled their minds. Once again, thanks for explanation.

A picture of the dyno tech's inability to open the hood

thatman

iTrader: (4)

Yeah, Definitely something I can tell them to do about not doubling the RPMs for my car!

funkjaw

iTrader: (3)

So what mods are done to your car?

flamve

Full racing beat "true dual" exhaust
blitz air intake
Emissions Strip
P/S and A/C Removal
Electric Fan Conversion

thatman

iTrader: (4)

^And royal purple...that accounted for the 1 extra Hp the second run...

funkjaw

iTrader: (3)

Yeah that seams right with the mods you have. Good stuff man.

itschrisfoo

yea i had the same problem when i got my car dynoed. its either the dyno was calibrated off or they put one of the wires over the wrong spark plug wire. my first run i hit 130whp with the same as you around 50 trq. couple months later with more mods to the car i hit around 160whp with 120trq, na on stock ports

flamve

Cool, glad to here that I am not the only one that had this kind of problem. Another thing that I noticed when I was going over the printouts that he gave us, is that he had the RPM going all the way up 14,000, which is false. When all is said and done, I am pleased with what it makes, and I am going to start get on other projects. Probably either get the GTO running or do some suspension stuff on the RX7.

thatman

iTrader: (4)

It sure didnt feel like 36% humidity....

flamve

As some of you may have guessed, Thatman is my errand boy, mainly because he owes me money for his crotch rocket, THAT IS STILL SITTING IN MY DRIVEWAY WAITING FOR PARTS. And anyways I was showing the 14k rpm, not the humidity.

FelixIsGod29X

iTrader: (50)

Are your aux ports opening/close properly????????????????????

flamve

I did a visual check of my 5th / 6th ports before and and after I installed my racing beat header, so I do believe that they are opening and closing properly. Do you think it would be worth my time to electronically activate them, since I don't have an air pump anymore?

funkjaw

iTrader: (3)

If they are opening than it wouldn't be worth your time to electronically activate them since the end results wouldn't be any different. However if they aren't opening than yeah it would be worth your time to get them working however you want to do it.

Tazio

Quick note. Because of the way hp and torque are calculated, they should always be the same at 5252rpm. If they're not then the dyno or whatever is set up wrong.

If the RPM is not reading right, it's likely because the operator set the tach pickup for a 4 cylinder (or something else) instead of a 6 cylinder.

1.3litre

I had the opposite problem the second time I went to dyno my car. My car put out 13 hp and 1000 ft/lbs, so I had them print it out for bragging rights. In reality my car puts out 145 hp and 12something ft/lbs, but 1000 ft/lbs of torque seemed right according to my *** dyno.