Lay it on the line - Rear Wheel HP - ITS 2nd gen

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ITSRX7

New member
OK folks here is the deal: We just took our 2 7's to a chassis dyno. The 04 car has a boneyard (80K mile) motor with all the bolt ons. The 05 has a 1 season old Speedsource motor.

The purpose was to see how much more the SS motor put to the pavement than the boneyard motor to see if we wanted to swap units. We only have one "right" diff and we need to optimize one car...

My question is simple: what HP numbers are ITS 13B's putting to the wheels? SS says if they build one for you with exhaust and fuel tweaks, then you should see 175 RWHP...

Anyone close to that? Should be no reason to keep this info close to the vest if you are legal, right???

Andy Bettencourt
Nick Leverone
Steve Ulfelder
Steve Ostrovitz

NER #'s 04 and 05
 
Just curious, which one had more horsepower and how much difference was there? I run a fairly stock motor with a few minor tweaks but I've never dyno tested it. However, I can pull the Z's that I race with on the straightaways.
 
If you have never had your car on a chassis dyno, these numbers will mean nothing to you:

Boneyard motor: 171.1
Speedsource: 163.5

Yup, that is right!!! We were shocked!

Now about other cars in ITS:

I have called all the major engine builders and here is what they said an ITS legal motor can put to the ground if they built it - allow for some 'fudge factor':

Bimmer World: 210 RWHP E36 325
SpeedSource: 175 RWHP 2nd gen 13B
Rebello: 170 RWHP 240Z
Porsche guy (forget his name): 185 RWHP 944

So by pure power to weight, the Z and the E36 are right up there...

Thoughts??? POST YOUR DYNO NUMBERS!!!

AB
 
Thanks for posting yours...

Sorry, mine are confidental..
smile.gif
Just kidding!

Seriously, my car hasn't fired yet, so no dyno time obviously. I'll have numbers some time this summer I expect.

<jaw hanging open on your results>

PaulC
 
Remember that, since the data comes from different dynos, run by different people in different conditions, it is not entirely correct to compare, but this IS an interesting question. For the sake of comparison (second hand info, as well)...

** 88-91 Honda Si (CRX or Civic HB) in ITA = 121-125 whp (Jackson Racing)

** Nissan Sentra SE-R in ITS = 153 whp (Speakman-built, Sunbelt-tuned)

The relatively poor performance of your SS roto-motor might have been the result of failure to adapt a more narrowly tweaked engine to changed atmospheric conditions. As you optimize engine set-up to increase output, you may well tighten up the range of conditions that it will tolerate without readjustment... Just a thought.

Kirk
 
Interesting point. DynoJet dynomometers are supposed to be pretty well even - taking into all the variables and compensating for them.

As far as the SS motor, there are very few variables between set ups. Understand that we are talking legal IT motors here and with FI to boot. We tested at a variety of coolant/oil temps and can say CONCLUSIVELY that (with Mobil 1) anything over 200 degrees in oil temp HINDERED HP output.

COME 'ON - POST THOSE NUMBERS!

AB
 
I here that the bone-yard motors WILL be better from all of the years of running, and not revving at high rpms. The long break-in time, and the years of smooth polishing of the apex seals to the housings will make the difference. I'm not surprised. Did you do a compression test on both engines to see the difference? Same exhausts used on both tests? If not there will be a difference. I've seen a used 1st gen engine with a compression in both chambers near 130, and it was used, warmed up to 180 degrees, and checked with the throttle wide open.

Shift @ 8000 RPM to win, or shift lower to make it last.

Any takers?


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Corey L. Clough
Ex-1st Gen, Pre-2nd Gen
[email protected]
 
Same headers, different straight pipe. We do feel the boneyard straight pipe is better designed but not 10 RWHP worth, that would be crazy.

Compression on the boneyard motor is lower than the SS motor. Mid 6's vs. mid 7's.

AB
 
Pardon my ignorance, but what is mid 6's? Is that 60 psi from the leading chambers warmed up and W.O.T.? Say it isn't so!

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Corey L. Clough
Ex-1st Gen, Pre-2nd Gen
[email protected]
 
Maybe the SS motor is "depressed" being in the 05 car and all!Does Andy drive the 05 car? Might be something there! I've got a JY motor with a layer of grime that says 175RWHP all over it!Willing to swap it for that SS and $500!
wink.gif


Brian B
 
When I say mid 6's for compression, this is a way to read it on rotories. If you have a compression test at a Mazda dealership, that is the form they will give you the data in.

Low 9's are new, mid 3's are about dead.

AB
 
What are the factory compression gauges displaying? kg/cm^2? bar?

Anyone with knowledge of leakdown numbers on a rotary? Numbers on my friends 12a(my old car) were scary low...(high leakage). I want to assume that since the rotors are not spinning that the apex seals are not sealing as they would while running...where as a Pissed-on motor's rings will seal very well while static. Any logic to this?
 
i'd rather go with the old compression scale. if is is below 90psi, it is about ready for rebuild. Suit yourselves. I'm new to this way of thinking, but what does a chamber that cranks out 100 psi rate on that scale?

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Corey L. Clough
Ex-1st Gen, Pre-2nd Gen
[email protected]
 
Andy. We need to talk. If you dont recognize my name, ask Nick. 407-889-7207 work, until 4pm. 407-889-7207 at home. Call me.

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Marc Dana
#63 ITS Mazda Rx-7
#77 STS BMW 325I
 
My old ITS RX-7 used to put out 187 to the rear wheels. Completely legal. I spent over 40 hours on the dyno with it.
 
I think it important to remember that you are comparing ,not just engines ,but complete drivetrains, fuel,ignition,exhaust and intake systems! I can think of at least 20 small things that could mean 10hp. I believe that Compression tests can be misleading, that rotary rngines seal better with RPMs.
The real question is what HP should a legal 13B develope at the RW's? Depends on the whole car. I think 175RWHP would be great and "affordable".Beyond that takes money and alot of massage time on the dyno. BB
 
Dyno sheets for my SS built motor (when it was 1.5 years old) was right around 176. It sounds like SS is at least giving accurate estimates.
 
I am VERY confident that SS is on the up and up. I have had a couple lengthy conversations with them and get a real good feeling that they know what they are talking about and are being straight.

AB
 
Originally posted by Rob May:
My old ITS RX-7 used to put out 187 to the rear wheels. Completely legal. I spent over 40 hours on the dyno with it.
Click to expand...

Rob,

I am interested to know if you found most of your gains from the buildup of the motor itself, or from the tuning process on the dyno. Email me at [email protected] if you don't want anything online.

I'm not looking for specifics (or speed secrets!), I was just wondering if there was more potential in the motor than in the tuning. Thanks.



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Chris Wire
Team Wire Racing
ITS Mazda RX7 #35
 
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