NASA PTD Race Car Dyno Results
 

I posted this a few days ago in the dyno thread in the "Tech" section but figured since it's a race car more people might find this information useful in the "Race" section.

Ok, had my NASA PTD RX-8 Race car dyno tested today for a "Dyno Certification".

Dyno was done at basically sea level on a Dynojet Dyno using "SAE correction factor 0.98" 70 F out and clear.

Three runs results:

Run 1 - 209 HP 136 TQ
Run 2 - 207 HP 136 TQ
Run 3 - 205 HP 136 TQ

Motor Modifications:

Pineapple Racing Built Motor with half a race season (~20 hours) and 1000 miles
Very mild porting (essentially the Racing Beat port)
Racing Beat Reflashed ECU (Stage "3" flash for ported motor)
Ceramic Apex Seals
Mazdaspeed/AEM intake
Racing Beat Exhaust Header with runners extended 1 additional foot in length
Midpipe (no cat)
Racing Beat Dual Exhaust
Light Weight Flywheel with Tilton Clutch
Torco Oils
Stock/OEM Pullies
No Air Conditioning

Dyno graph attached.

The only thing that was a suprise to me is how lean the motor runs. The AFRs were in the 14.30 to 13.5 ratio even in the meaty part of the powerband. The dyno shop does a TON of dynos and assured me the AFR readings were accurate.

Been running the Racing Beat ecu reflashes for years with no problems so I'm not worried - I've just never seen a car run this lean on the dyno.

- John

Thanks for sharing. I dynoed mine for classing purposes but the n00b in me didn't read the instructions correctly and did it on a Mustang dyno, so I want to get it redone.

On the Mustang, max readings were 186HP/132ft-lb. I use RB's "race" flash (stage 2?) and the reported AFRs were much leaner than what I have logged through the PCM in the past. Either theirs is wrong, mine is inaccurate or both.

I'll report back once I get mine dynoed on a DynoJet.

yes the Racing Beat stage 3 flash does cause what you would normally think of as "lean" afr's. I noticed this 2 years ago when a good friend of mine was running TT with Nasa.
I called them to be sure it was the flash and not something else and was told --dont tune the rotary for afr--tune for power. Yep--I was told that. This is of course is for the na engine only.
keep the coolant/oil temps down!

if they didn't screw in an O2 meter up by the manifold then there is likely air being pulled into the exhaust system, it's pretty common

high 13s best power, but at the expense of engine life

low 13's much better engine life, but only at the expense of several HP

what are your compression readings?

edit: I've run 14.7 WOT on the dyno multiple passes, it won't blow up really, but eventually the side seals will pass on to another life of junkyard scrap


.

When I took mine to the dyno, they stuck a foot-long probe in the exhaust tail pipe. I was thinking: "How's what accurate? Well, they are the experts...". Once again, I was wrong thinking I was wrong.

I don't see the point of the Racing Beat ECU solution. It's too bad you didn't have another RX-8 to run on the same day to see the comparison.

For those of you who run in NASA and are considering a Dyno Reclass...

The national director, Greg, keeps his "formula" for dyno reclassing rather secret. Kind of like the Coronel or Coca Cola. :)

So... I was assigned a minimum competition weight based (with driver) as follows:

At 215 rwhp 3095 lbs min comp weight

At 213 rwhp 3065 lbs min comp weight

The "base" minimum competition weight for the RX-8 in NASA PT is 3045 lbs

It's good to add on a few more HP in case you go over a bit if you are dyno tested at the track. Don't want to get disqualified.

This dyno reclass should help me as it eliminates all "points" for motor modifications (exhaust, intake, etc) and my car is overweight (or maybe just the driver!) anyway. I'll probably run at the 215rwhp / 3095 min weight level.

I now have enough points available to stay in PTD and run the BFGoodrich R1-S tires in a 235/40-17 size. BFGoodrich has a good contingency for NASA racing so we'll see how it goes!

Unfortunately I don't know. I tend to run my motors until something breaks... I then put on a standard compression tester with the one way valve removed and watch the "bumps" and say "oh yeah... look... it's toast!".

A "real" rotary compression tester is hard to find!

I got three seasons out of my first motor (and that's racing in three different race series so it's almost like five seasons!) but only about one and a half seasons from my second motor - but it was used to begin with as I couldn't find new parts due to the Tsunami. So far so good with this motor.

I'm just a shade tree mechanic / amateur racer doing the best I have time/money for.

- John

MagnusRacing: I went through the same obscure, esoteric process. I got TTD* (+7 points) with 207HP max and 2,900 lbs min weight.

Although my shocks/springs are "street" type, I still get hit with points as if they were AST 5100s or Koni 2812s. Anyhow, I am going back to 225mm wide tires to be in class (-4 points) with NT01s.

In our first event of the year, car and I weighted 2,930 with 3/4 tank and a big dinner. Since a cage is being welded in, I wonder how it will affect weight (est. 130+ lbs, minus trim, sunroof, heavy leather seats, etc).

Just depends on the cage. Mine is super heavy - but since I do rally racing with the car too it needs to be crazy strong and accomidate my navigator. It actually ADDED weight overall even after I fully striped the car. That combined with my 250lb personal weight makes me porky.

I'll tell you what I would do if I had your car:

Best "non external reservoir" shocks I could find (I like Ohlins) +3 points
Race Springs to your liking +2 points
Stock everything else including sway bars (with stiff springs the stock sways seem to work ok)
Hoosier R6 225 tires + 6 points

Total: 18 points

At 2900lbs and 200ish RWHP that would make one quick TTD/PTD car.

I love the NT01s as well for the value but the Hoosiers really are faster plus they have a contingency program. If you have at least five competitors in your class you can win a full set of Hoosiers each weekend as well if you win both days.

I hear ya! My budget can't take Hoosiers right now while still developing the car. Contributions are welcome :-)

I hear you... last year I knew I probably wasn't going to be able to "win" any Hoosiers through the contingency program so I ran on NT01 tires. Last twice as long and cost half as much! (almost!)

This is interesting to see what other people are getting on their dyno reclasses... the more I see it the more I think that there isn't a set in stone formula that gets used.

I'm rebuilding my engine right now as well as changing a ton of other things but will be in Time Trials C class. Most of my points are going to be for tires and aero, I'll be maxed out in points. Main points mods are 275/40R17 Hoosier R6 (I'll be mostly on 275 NT01's unless I think I can start winning, I made sure to have points for the Hoosiers, usually have 7 to 10 people in TT-C at events here), front splitter, rear wing, canards, side skirts, vortex generators, rear diffuser, coilovers, and sway bars.

My options were:
Base Class / HP / Weight
TT-D / 200 / 2935
TT-D / 210 / 3025
TT-D* / 218 / 3055

I thought about emailing him back to see what I could get the weight down to with a TT-C base class but I think it'll be fun to try and compete against everyone else using a different angle of attack, which would be a lot of tires and a lot of aero to make up for my power to weight disadvantage.

I'm shooting for 210RWHP at 3025lbs. Means I can keep the power windows and locks etc. LOL.

arca, you don't daily your car do you?

I did until the front main seal started leaking about a quarter of a quart per session last October at the track. Has 106k miles on the original motor, still ran fine though, was just a little tired and I wanted more power up top, it only made 174 on a dynapak but still had 145ft-lbs of torque. It then sat on the side of my house for 3 months and now it's in the garage and the motor is out. Needless to say converting it into a racecar happened way faster than I had anticipated. At first it was just some bolt on parts then one day the interior was all out, then the next thing you know, cage, fixed back seats, harnesses, etc. and before I knew it I was standing around asking what the hell happened haha.

I've watched that movie somewhere else. The epiphany came when my wife asked: "Why don't you get another car as a daily driver?"

Can the rx8 really complete in TTC?
I found that the 275's actually slowed me down a little. 245's-255's ( hoosiers only?) seem to be the best size for my car. I guess each one can be a little different.

Not scientifically proven but most people I respect agree that compound is more important than width, specially in TT, obviously to a certain extent.

Interestingly enough, used 255/40/17 NT01s+17x9 Enkei RPF1s weight the same as new 225/45/17 NT01s+17x8 Enkei RPF1s. Yet, again non-scientifically proven, MOI on the 17x8 set should be better given where the additional weight is on the 17x8 (ie hub).

From what I've gathered, I'd rather get to TTC due to lower weight than due to wider tires.

If this doesn't make sense, whatever... what do I know? Too many beers.

Yes, an RX-8 can compete in TTC/PTC at tracks that don't favor high horsepower if they are very light and have a very healthy motor. Some of the "Mother's Wax" guys in SoCal do pretty well in PTC in an 8. But is it the "ideal" car for TTC/PTC? No.

ok thanks for the info and that makes sense.
The tracks around here favor hp unfortunately--road atlanta, Roebling, Barber with Barber being the less hp advantage one.
good Luck guys and rotor on.

Is the intake tubing on the AEM the same diameter as factory?

No. Run a quick search on the "Aftermarket Performance Modifications" forum for further info.

Yeah part of it is the way my dyno reclass came back since I'm porting the motor and it's mandatory, I guess I could ask for a TT-C base class to bring the weight way down but then I wouldn't have enough points to do other things I was planning on with the car without getting into TT-B territory where I'll get annihilated either way. If I was trying to be super competitive in TT-C then sure I might have gone a different route but the long term goal is 350+RWHP with a naturally aspirated 20b with a focus more on Time Attack, and wherever it falls in NASA TT doesn't really bother me. I think it'll be fun using a different approach to try and lower lap times. Most of the guys here are lightweight with good power to weight ratios and minimal modifications and smaller tires, I'll be in a heavier car with big tires and lots of aero. Also there's only a couple high horsepower tracks in our region so we'll see how that goes.

I like this thread. Perhaps, we should have a NASA PT/TT thread (a-la STX thread)

I thought it may be. But if it's not and the RB Flash doesn't correct for the MAF readings then that could be one of the factors leading to a lean A/F ratio.