SCCA RX7 RACER

Dyno Run Sept 2 2008
1988 Mazda RX 7 E Production Prep Car
9 am B.C. Canada Air temp approximately 12-15 Celsius
4th gear pull with stock turbo 5 speed (Tail shaft needle bearings) lightened clutch and a posi 4.88 gears in stock rear end 225 50 R15 RA1 Toyo Tires

Street Port SCCA standards (off internet). 3 “air intake KN to stock 13B S4 throttle body ported stock intake runners and in take manifold. Small change to exhaust port, true 2” ID headers to a custom made 3” stainless exhaust with a special made muffler (Below 95 db at track with cloud cover sound came in at 94.4db)

Megasquirt system MS1 with V-3 board missing teeth CAS with 450 Primary and 700 secondary low impedance Fuel pressure set to 42psi high volume fuel pump.

Stock 89 to 91 rotors and shaft stock seals and bearings turbo oil pump (Oil pressure under load 93PSI) Limit shifts at 8500 RPM (Have gone to 9000 in two races to see if it would go pop but did not only a test) AFR used 13.2 to 13.4. Max under full load. LC1 wide band located at two in to one header location.

Note running for several years never repeat never lost an engine.

Fresh engine MAX 196 RW HP and 194 RW HP after it loosen up should get about 3-5 HP more. I have one small trick to try on the stock intake system that falls in to the rules of my class. I feel it is only good for 3HP at top end. So based on what I am allowed to do I am at my limit. Sorry.

This program is good for cold start up, driving around the pits and Fu#@ hard on it from 5200 RPM to 8500RPM. I hope this help a few on setting up mid to wide open throttle.

SCCA RX7 RACER
BTW: Set new track record in class this past weekend (Two first and one third place finish)and set personal fastest lap.

SCCA RX7 RACER

Tring to Post Program (Attachment??)
OOOPS my son told me to put it in what they call a zip file.
I'm good with race cars but not stronge with computer stuff.
SCCA RX7 RACER

SCCA RX7 RACER

Data LOG 1st to 4th gear on Dyno.

Attachment more info to look at.



I'll try and scan the Dyno run at a low setting so I can post it.

SCCA RX7 RACER

Here is Dyno Run
http://phishcave.com/upl/eJAOcR9wBt.jpg

riptyde

iTrader: (5)

I like the power curve on that. Do you think that a S5 intake with the vdi setup would be benefical for a little more top end? Great #'s.

SCCA RX7 RACER

There is no major benefits to using a S5 intake system for mid range to top end power. The purpose for the longer intake system (S5) is to increase low to mid range torque. Measure the distance and diameters of the S5 system and compare it to the S4 system. You will find that the distance of the intake runners from the base of the throttle body manifold to the centerline of the intake manifold on the S4 system is the same distance as the S5 system from the air flow valve to the center line of the intake system. This area is the most restrictive part of both intake runners and are almost identical. Most racer use the S4 system because it is easier to cut them open and port them to the maximum. Remember the shorter the intake runner the more suited for top end power and the longer the intake runner for low to mid range power. That is why Mazda set up the valve on the S5 system. As the rpm increase then the air valve opens to create a shorter air flow run from a larger air source. The 4 rotor engine that won Le mans had the intake runners extend and shorten through the RPM range to improve low to mid range power.

Good question I hope I answered it correctly.

Happy tunning
RX7 RACER

peejay

What are you running timing-wise, if I may ask?

SCCA RX7 RACER

I will try and attach a screen photo if you do not see it posted just open up my program that is labeled Mission a few threads up. It will be in there.

My idle seams to float up and down a bit (+ - 150 RPM) it is set to 1500 RPM at a AFR of 12.7 seams to work the best. I feel it is because i have a very wide spread in rpm at the low end. I did this to give me a better tuning range at certain RPM s to have sharper throttle response coming off the corners. My range at the race track mid corners and out is 4500 RPM to 5700RPM. You can see a wider rpm spread range from 6500RPM and up. The reason for this is I found is that my TPS tells me I am always WOT above 6500 RPM unit the next corner. At this point due to the restriction of the porting of the intake runners (SCCA RULES) the air flow is limited. So the volumetric efficiency decreases as the RPM increase due to this limit and of the street port. Having the air flow limited the variation of fuel to air remains very constant at the top end. At the upper end I do not need small 500 or 250 RPM increments to control the AFR.

I have found in my case timing not to be as critical as the AFR mapping. Do not exceed 26 deg total advance (NA engine) zero HP gains.

I have a friend that builds race cars 2 and 3 rotor fuel injected PP NA engines, sequential gear box ECT. On the same dyno I used he can pull at the rear wheels 396HP at 7900 RPM with the three rotor.. It will rev to 9500 RPM but at the time he only had a few hours on the engine for brake in time. I mention this just to let you know that I run the same timing as his PP engines and they are all limited to 26 Deg. He has been building them to race from when the rotary fist came out. This guy knows he is 75 years old and has count less championships under his belt.


Best Regards,
SCCA RX7 RACER

peejay

Interesting. I'm running 27 leading and trailing, locked timing. It really likes it but it doesn't idle so well. (Oh well!)

It looks like I'm leaving a lot of power on the table. My fuelling is in the 12.0 range up to about 7000, and then it richens up to 10:1 at 8500. (My map ends at 7000, only dyno tested it to 8500, but it sees over that, haven't bothered to re-set my RPM table after switching from GSL-SE to the un-turbo) I wonder how much more power I can get just by pulling some fuel out. I had set it up on the rich side because I'm worried about keeping the engine cool on 40-80 second runs, but if you're circuit racing, then maybe I'm just worrying too much.

On the other hand, I'm making slightly more torque earlier, which is unexpected given the shorter runners of the TII intake manifold. (I assume that this option is verboten for your class)

SCCA RX7 RACER

I do not have any short runs to post while I was on the track. I found running hard in races from 30 minutes to two hours was the following.

Any time I was below 12.5 AFR I could feel the car ran slow off the corners if it was at 10 to 11.5 it felt like it was missing (Drowning). On the top end due to the lack of all out torque and gearing to pull through the air at speeds over110 MPH (My car will not pull more than 142 MPH at the end of our longest strait at Spokane Washington track) I could not get the same feel in the seat of my pants. I found the best way to adjust my fuel air was shift point markers at track side and max RPM at the end of the tracks longest straits. Through time on testing at the track and full throttle chops to read plugs. I found the limits and were backed up by fellow rotary racers. If you have a NA engine go for 12.5 to12.7 with 50% to 75% load and throttle at 60% to 75% at around 4500 to 5500 RPM s. Then as the RPM climbs and your at WOT with full load lean to 13.2 to 13.4.

I have set new track records at 3 of the 4 tracks that I have run at in my class. If it works for me I would say it will work for you.

Play with confidence.

SCCA RX7 RACER

toplessFC3Sman

iTrader: (1)

SCCA, your spark table looks pretty close to what I have at 100 kPa, but below there and above 2k rpm you could advance timing a bit and gain some more power for those times when you aren't WOT. This will also help a bit with part-throttle fuel consumption (which is probably not your primary concern, but if you can squeeze another few laps out of a tank, thats always a plus). If you look at the area of my timing map below 100 kPa, you can see what I mean. When the fuel/air charge is less dense (lower pressures) it takes longer to burn, so you need to fire the spark earlier to get the peak pressure to happen at the correct time to get the most power out, as well as to have most of the combustion complete while it's still in the combustion chamber.

peejay

I'm at WOT as low as 1500rpm in street driving... (It makes a tad over 100lb-ft at the wheels there, that's more than a stock 12A made at peak, at the crank!)

It takes very little throttle to get to 95kpa (local atmospheric).

I'm really not super concerned with power at 9k, that's just where the RPM goes when the tires *really* lose grip. So if it drowns in fuel, so much the better. I'm more concerned with the midrange, at least until the money tree is ready for picking and I can get a close ratio sequential gearbox, and a truck and trailer to haul it to events instead of driving it, and a house with enough room for a truck and trailer... makes more sense to just make more power in the midrange

SCCA RX7 RACER

To help slow down the rapid jump in vacuum response time. I took a small plastic in line fuel filter (Lawn Mower Type) cut it in to two and removed the filter screen I then took a compressible strip of foam and packed it in and wrapped it with black electrical tape to keep it from expanding and to push it,s self apart. From trail and error I packed it with enough foam to slow the signal down. The TPS signal in some cases matches the MAP signal. I found with this set up that the MAP had way less jumping from the bottom to the top with the throttle response. This allowed for easy tuninng on smooth throttle openings when coming off the corners. Try it cost $3.50 1.5 hours of time. I located 18 inches away from the MAP sensor.

Best Regard
SCCA RX7 RACER

peejay

I just run a vacuum hose.

I also need almost no TPS enrichment, either.

SCCA RX7 RACER

[QUOTE=peejay;8544923]I'm at WOT as low as 1500rpm in street driving... (It makes a tad over 100lb-ft at the wheels there, that's more than a stock 12A made at peak, at the crank!)

It takes very little throttle to get to 95kpa (local atmospheric).

Peejay if you slow the vacuum response time it will help you tune your mid range through your RPM range. In this way as you feed in throttle it will not spike to 95kpa. I think from your message I quoted that is what you are dealing with. But if it works all right for your application keep on tuning. 100Lbs at 1500 is very strong number for a 12A.

Best Regards
SCCA RX7 RACER

peejay

It doesn't spike... it stays there. Sorry if I wasn't clear.

It's a mishmash 13B, not a 12A. (It's originally a 12A chassis, so stock 12A is my benchmark) 13B Turbo housings and intake manifold, 9.4:1 rotating assembly. (Not anything legal for the stuff you do) The throttle assembly was tweaked so that all three blades open at the same time. Currently it holds atmospheric pressure all the way out to redline, if it did not, i have a 75mm throttle body that is nearly a bolt on, aside from having to remove the divider in the plenum.

I am going to try to do something to slow the vacuum response, only because the pressure pulses are noticable at WOT and it makes the tuning irregular. TPS based would be ideal for that, but the downsides aren't worth it in my opinion.

HadaGSL-SE

iTrader: (6)

SCCA Racer,

What code are you running? MSextra 29V? MS Extra 29V4?

Also which two cas teeth did you cut off? I am getting ready to install my MS and am planning on using your map as a good base.

P.S. Were you at the Runoffs in Topeka? I didn't make it with the magazine but I was at the NASA Nats.

Thanks,

Greg

SCCA RX7 RACER

Hi Greg

I am using MS1chip with 029Q code.

I cut the two teeth at 90 deg from the top two teeth it made sense because of the easy access. I remove the electrical but left the rest of the CAS together and had no problem grinding them down with a 1/4” die grinding bit.

I have not gone to the run offs due to the travel distance here in the Pacific Northwest area.

Take your time and do a clean job on wiring and you should not have any problems.

Best Regards
SCCA RX7 RACER

HadaGSL-SE

iTrader: (6)

Thanks for the info. I may have so more questions once I get to wiring.

You might consider joining NASA. The nationals are moving to Utah for the next two years. I am not sure how far that will be. Also I am sure you've heard that SCCA Runoffs are going to Road America in Wisconsin.

Thanks again!

-Greg

SCCA RX7 RACER

Hey Greg

Be certain to rewire every thing. Take time to rubber mount the Megasquirt unit on a good base plate and locate it in an area that has good air flow around it. Be certain that the DB plug in cable has good support on to the base plate to eliminate any connection problems from vibration in side the connector. Also isolate each circuit and use proper rate fuses. Also on the out put cable allow away of being able to test each circuit for easy trouble shooting later. Take the time now will save you hundred of hours later.

Best Regards
SCCA RX7 RACER