Hello Everyone,

I posted this is the RX7 Tech Support section but I thought I might get a little more visibility here

Hoping you all can help me track down some missing HP. Here is the 411

Recently got a Gtech pro and using the RWHP calculation feature, I was only able to muster 204 RWHP.

Using the formula I've seen before (1.17) for drivetrain losses I multiplied 204 x 1.17 for 238 fwhp.

The test vehicle:

'95 base model Automatic
54k miles (not rebuilt as far as I know)
Downpipe
Greddy SP CatBack
Gutted Cat's
Pettit Silicon Hose Wrap
Pettit Tune Up 2 months ago (fuel filter, plugs, etc)
Pettit Alum AST
Pettit Power Pulley
Boost pattern 11-8-10 bleeding to 8 at redline
14" hg vacuum at idle (850 rpm)
18x8" SSR Rims


Test environment:

Elevation: Sea Level
Temp: 85
High Humidity
(Miami Florida)


I ran the test as per Gtech instructs, level road, correct vechicle weight. Using the "Hold" feature to shift at rev buzzer.

Shifts seem pretty tight, but I dont have any experience to go on.

I figured I would be at least 225 rwhp or so. Any ideas?

I know the Gtech is not entirely accurate and getting the car on a dyno would be best.

Is it the high temp and humidity robbing power or my automatic transmission

BTW my best 0-60 time was 5.8 sec. Powerbrake till 2500rpm

Thanks for the help!

 

From what I've heard from others, the g-tech is accurate only in its ability to be off.

Even the automatic can pull more hp than what you got, especially with the mods....unless of course something is wrong with your car.

 

I have a gtech also, as well as an automatic. I never did the HP measurement, but I frequently did the 0-60 and 1/4 mile times. What did you get for those? From what I have read, the first gen gtech was pretty inaccurate, but was supposedly better by 2nd gen, though the results were a bit optimistic (I think it was Car and Driver who reviewed it). Anyway, I have a DP, catback, K&N, power pulley set and my best was a 13.6 1/4 with a 5.2 0-60. Usually however, it was high 13's low 14's, which is what the 5-speeds run stock. Expect more driveline loss with an automatic. I also heard a rumor about the torque converter limiting the power output. I don't know if this is true. I bought a new torque converter with a higher stall speed, but I haven't found anyone to put it in yet.

 

i think you have to tell it the weight of your car for it to calculate the RWHP number. how much did you say your car weighs??

 

My best 0-60 time was 5.8 sec. That was done by power braking to 3000 rpm or so (around 5 lbs boost). And using the "Hold" feature to shift at redline.

As im sure you auto owners know, off the line performance is dismal at best.

If I did a normal start and didnt use "Hold", just letting the tranny shift normally I averaged a 6.6 sec 0-60.

As for the vehicle weight. I looked on the VIN door stamp and subtracted 180lbs for the missing passenger. If I remember right it was around 2750lbs or so.

My next mod will most likely be a Intake and then 4.33 gears. Save up and wait for the automatic to give out, then swap a 5sp.

The problem is Ive never had the chance to drive a 5sp FD, Im sure if I did I wouldnt be able to sleep until got the car right.

Dont get me wrong Im not bashing Auto's, If they're done right they can be sweet, but the difference between a stock FD Auto & 5spd is just to great.

Thanks for the help

 

You don't hear of many "very" fast auto FD's. Their transmission shifts nothing like the Supra TTs. I think stock from the magazines were 0-60 in 6.0-6.5 secs and the 1/4 in 14.5-14.8 - nowhere near a 5 speed. Most auto FD's reach very high 12's - low 13's with a long mod list - just not much capability with the auto.

 

if you read about the g-tech accuratcy for hp you will see that they state if you have a turbo car it will read low. Man!! Am I the only loser that reads instruction manuals before using

 

Automatics are still very fast, the only problem I have been having is finding a ECU for it. Anyone have any suggestions on where to look? I have a cold air intake and 3 inch full exhaust and am scared to get the intercooler until I find one. Any help would be cool.

 

unix,

the gvwr for the auto is 3275. I don't think this includes the passenger, so you should not subtract 180. In fact, you should
ADD 180, since the measurement is taking place with you in the car. So try 3450 and see what you get then...

 

oh yeah, has anyone ever heard of an auto with non seq conversion, or a single turbo? In answer to the ecu question, rotary performance told me they can wire a haltech to an auto and it will work, but plan on a little over $1K for the haltech plus a little over $1k for the install.

 

hmm,

Ya I see the weight is 3275 on the VIN stamp, but it also reads on another sticker that 3275 includes 366lbs for driver and passenger. So I subtracted 183 from 3275 which is 3092

I messed up in the previous post when I said 2750 or whatever it was...

About the ECU talk, Its my understanding that you can use pretty much ANY aftermarket standalone ECU just as long as you wire it up right for the features you want to keep. (Meaning you would have to keep your existing ECU to control the tranny)

EFI/PFS PMC (purple) piggyback computers work in auto's fine and can be had for around $500 or so on www.thepartstrader.com.

 

I have been looking for an ECU but everyone I talk to tells me that I will lose my HOLD function and that the HOLD light will stay on all the time. I don't know if I can stand looking at another light in the dash, I have a hard enough time keeping my eyes on the boost guage and temp guage all the time.

 

Wow. That's really sad. With my lightweight flywheel I blast through first gear, accompanied by wheelspin and a deafening roar (esp. under an overpass ). Many of my stoplight races with corvettes and other high-hp cars have been won in first gear.

Get a 5spd man, you're missing out on all the fun !

 

Negative. An FD weighs ~2800 stock. An auto tranny would add some weight, but not that much. With my current setup (no precat, cat, airpump) I'm at just over 2700. Somewhere around 3000 lbs. seems like a safe number to use.

I would just find a dyno. I've used the G-tech and it was almost a waste of time.

--Rich

 

WHAT? You think I made that number up? That's straight from the sticker + the owner's manual. The R1s were light straight from the factory, but the touring models had a lot of heavy refinements.

 

The GVWR is the Gross Vehicle Weight, that is the most you car is rated to weigh with passengers.

Unixpilot did it right but the most accuarate way is to just have it wieghed. Most drag strips have scales you can weigh your car on then add you weight to that. Also figure I think 7lbs per gallon of fuel you have in the tank.

I got real good results with a GTech but its only as good as the data you enter. It required almost perfect data and perfect enviroment to be real accurate.

On a side note I do think that you should have you torque converter checked out. I think they can only transfer a certain amount of power and its not much over the stock 3rd Gen power.

You also NEED TO GET A ECU UPGRADE NOW!!!!!!!!!!!!!!!!!

Later,

 

Thanks for all the help guys... (SPOautos)

I know I cant go any further in mods (DP, CB, High Flow CAT, Power Pulley) without the appropriate fuel mods (ECU, Fuel pump, etc)

I want to get a A/F meter, even though I know those arent to accurate either, just to monitor things now.

The car runs real rich, smokes a little blue for until its warm, then it clears out. But I get a nice black puff on a redline 1-2 shift. Plus it pops like a banshee during deceleration. Usually a quick series of 3-5 pops. No backfires or flames though

But the bumper and fartcan will carbon up if i dont keep it washed. Plugs were changed about 5k miles ago, havent taken a look at them yet.

Hey weaklink, or any other Auto owners. Whats the 411 on upgraded torque converters and such? Who sells em and how much?

Thanks again,

 

the pfc works in the auto car, i have one in my car. Yes you will loose the hold buttom, but i would rather loose that than to blow my engine. I'm doing a trann swap this fall I'm sick of the auto you loose a lot of power with the auto.

 

unix pilot,

1. I have the same mods as you. Right now my car is at RP where they are trying to install a PFC without losing ecu control of the transmission. I will let you know how that goes. You lose more than just the hold function if you abandon the tranny's ecu. For example the ECU retards timing during shifts. There are other things too that I'll omit for brevity's sake. A 2nd and more expensive option is a haltech, which I think Chris at RP said can be made to work WITH the auto ecu, but requires a lot of time and tuning(=BIG LABOR $$$). OH yeah, please understand these are my interpretations and I am in no way speaking for anyone at RP.

2. Level10 (www.levelten.com) makes upgrade kits for auto transmissions. I have mixed feelings about them. I bought one of their torque converters and a PTS upgrade kit. I got the runaround trying to get my parts. Nobody knew where they were. One person said they were shipped, they were not shipped, it was done, not done, etc. So and so handles that and he's not here, blah blah blah. Well I finally got them and they have sat on the floor in my study for about 3 months now. I don't trust anyone in town to do the work, mostly because none of them understand why I would want to replace a perfectly good transmission. (starting to feel that way myself) The torque converter was around $500, and the PTS kit $700. So right now I am just going to wait until something breaks and then have all the work done.

3. http://www.protorque.com/ has a good FAQ about torque converters, stall speeds, etc. Factory stall is around 3000-3200, mine from L10 is 3200-3600. Supposedly any performance transmission shop can modify your torque converter by machining it.

Sorry for the long post, hope it helps somewhat. If you order from L10 just plan on waiting a while. So do not PAY for express shipping of any sort. I also heard some guys on the supra forums had complained that they had premature failure with their transmissions-I don't know.

I can't get the soot off my rear bumper, even with weekly washes, and it's white! Sucks. Also do you have problems with a strange burning smell after you shut down after you had your high flow cat put on? I know it's normal at first, but it's been about 2-3K miles. It's not that sulfury smell, it's not exactly like exhaust either.

 

You may want to try to recalculate the HP of your car. I know that the automatic FD aren't as fast as the Manuals, but that doesn't exactly sound right. I would look into it a little more.

 

unix pilot,

hopefully I will have some dyno numbers when I get my car back. We have similar mods, so we can compare #s to your gtech.

 

Thanks for all the info weaklink. Precious stuff for a news hungry auto owner

Ive been eyeballing the PFC too. Im going to give Pettit a call ( I live in S. Florida) and see what they can do as far as engine/fuel management for an auto. Not sure if they offer ECU's for an auto.

Other than that, I guess I stick to my original plan and just start saving and collecting parts for the 5sp swap. From what Ive heard its gonna be around $3-4k

Wish I could just keep and upgrade that auto tranny and dump the 3-4k in more mods, but I've heard from too many people that there is really no point.

As far as the smell from the high flow cat. I've never noticed anything unusal.

Look forward to seeing those dyno numbers and congrats on your car!

 

If that smell is anything like a hot glue gun look under for a melted grocery sack under the car mated to your cat or exhaust. It will probably look like shiny goo by this point though.

Tsumi Kinetic
93 Montego