Nick86

iTrader: (1)

I had originally posted this in the SAFC section - but I got no responses, and only 5 vies, so I'm going to try and post it here!


Well, I have recently purchased and begun installing an SAFC (blue screen 4 button kind).

I have the following:
1986 GXL
12,000 miles on a Rebuild
Rebuild done with FD housings and a mild street port.
CAI
RB downpipe and presilencer
Dynomax catback

Stock fuel pump
Stock injectors
Stock ECU


Due to the S4's narrow range TPS I will be hooking the SAFC up to the either the N/A boost sensor or an S5 TPS that will get installed solely for the SAFC throttle readings. With either of these I hope to gain full throttle range as far as the SAFC is concerned. (If anyone has any thoughts of which setup is better - Boost/Vacuum sensor or S5 TPS - let me know!)

Once the unit is all wired in, I'll be heading to the local Dyno shop to have it properly tuned using a wideband O2 sensor.

Here's the probelm - the tuners at the shop are not too familiar with rotaries - and are not familiar with N/A rotaries at all! The guys there are great tuners of regular engines - but not so much mine. They said that they will tune the car to what ever specs I desire, but they don't have enough experience with rotaries to offer suggestions. So my question is:

What AFRs should I be tuning to?

I'm not looking for the optimum power that an N/A can put out (this is a daily summer driven car after all) - but rather a safe setup that will gain some power and especially smoothness in the upper rev range. Everytime I do a search I come up with either numbers for Turbo cars - or percentages that the car was leaned out. If someone could provide me with some Air Fuel Ratios that I could have them tune to - that would be a huge help!

Thanks!
Nick

wpgrexx

do you have the solenoid rack removed from the motor? ie making a little higher fuel pressure? I would lean things out quite a bit. When I was na I beleive I leaned out around -12 until 3800, just before the secondaries came on I was getting a lean spike, so I turned up the primaries just vefore the secondaries come on. Not much though. As for the upper rpm I leaned it out crazy.

The obvious suggestion of tuning on a dyno with a wideband comes up, it will for sure make a difference over tuning with the butt. It may help gas mileage a bit too.

Nick86

iTrader: (1)

Thanks wpgrexx....

Like I said - I will be tuning with a wideband O2 on a dyno. But before I go drop the money and time on that, I need an idea what AFRs I'll be tuning to.

You mentioned that you went -12.... but what Air Fuel Ratio did that correspond to? I don't want to just go in there blindly with SAFC settings - but rather a ratio that they can tune to.
-12 on your setup may be -10 or -14 on mine!

wpgrexx

thats very true. I was going off of a dyno slip with a/f ratios on it that I got from jimmi325i when I bought his motor. From that I made my settings. I personally never took it back to the dyno. I would think you would be able to lean it out very far, since stock is very rich.

Sideways7

iTrader: (7)

Do you have an A/F gauge in your car? They can be helpful when using an AFC. Also, you prob know this but make sure the people at the shop know not to tune your rotary like a piston engine. If you lean it out until you start hearing pings it'll kill your motor.

Nick86

iTrader: (1)

No, no A/F guage. But if I get it tuned on a dyno using a wideband - the need for a narrow band A/F guage is not as great.

That's my (and the dyno shop's) chief concern! He has already told me that he doesn't have enough rotary experience to be able to tune it like a regular piston engine - which is fine. But if I could say to him "A good Air Fuel Ratio at Y RPM is X." He can tune the SAFC to that AFR. The actual number on the SAFC (-12, -9, -88) is irrelivant. If their Wideband O2 says that I am running richer than that "X" AFR, then it can be leaned out accordingly. I just need to know what that Ratio is, and is it constant throughout the rev range, or does it change?

Idle: ?
1000: ?
2000: ?
3000: ?

7000:?
etc...

Thanks!

Kingofl337

alot of people seem to say 12:1 A/F because if the car runs warm and pings!!! DUNNNN NAAA NAAAA. Bye Bye motor.

Nick86

iTrader: (1)

Thanks!

Now, is that 12:1 on an N/A?

Is that 12:1 throughout the rev range or will it change?

Kingofl337

Yes that would be through out the rev range except idle would be leaner. I'm not 100% sure if thats for both N/A and Turbo. My experiance ends here has I'm new to the RX-7 community. I've been reading ALOT though. You might want to check out the dyno section above and looks at some N/A dyno plots with A/F graphs.

Update: After a bunch more reading the N/A's seem to like to around 14.7 at idle. Then drop down to mid to hight 13's accross the board.

Nick86

iTrader: (1)

Thanks!

I had seen some of the graphs and had dismissed them as either Turbo or S5...... but now that I think of it, an S5 NA is still basically the same thing!

Anyone else with some firsthand advice?

Kingofl337

Well a turbo has to run richer because of the heat involved and higher total compression then a N/A motor. Rotorys espcialy. 11:1-12:1 seem to be the TII sweet spots.

ddub

13's are a good AFR to shoot for. Low 13's most likely.

slvr7

iTrader: (1)

Nick,
Have you seen the article from Drag Sport magazine about carb vs. fuel injection on a 13B? There is some *interesting* discussion there about dyno tuning & AFR's. I have it as an acrobat file if you want a copy - just send me an email addy.

My own observations were that my baseline runs went richer at high rpm, from around 13.5:1 @ 3K to 11.5:1 @ 7.5K. Leaner will make more HP, but tradeoff is higher combustion temps @ high rpm which is worse for apex seal life.

Boost sensor vs. TPS - I'm sure you've thought of this already, but he TPS route is a bit tricky mechanically as you need to devise a mount that will depress the plunger full range.
Boost sensor goes to about 4V at WOT, but I don't know how low the full vacuum reading is. Would need it to be near 0 V, right? Seems like it might be too much trouble to map the part throttle values accurately anyway, especially when it's WOT where the fun / danger is.

1987RX7guy

iTrader: (3)

I'm no tunner by any means but I would personally shoot for 12.5-13.25afr with stock timing. But hell I dunno I am personally going to tune using EGT so :-D

scathcart

I tune 13.4:1 at peak torque richening up to 13.2:1 at peak hp on N/A engines, and 15.5:1 or higher for low-throttle.

88IntegraLS

Scathcart again shows that he's the man!

On my S4 NA with a street port, I attained maximum Gtech instantaneous g's by gradually adding in more fuel above 4k rpm, ending at about +14 at 8k rpm. My track trap speed improved by a couple mph because of a rough Gtech SAFC tune job, and my cruise mpg went up a mile or two . .

scathcart

Adding fuel above 4000 sounds about right if I remember your setup. Every ported N/A running a stock ECU and a S-AFC that I have tuned needed fuel added in the top end to keep from running lean.

I just finished tuning an S4 N/A which was running power-robbingly lean on the top end with a stock-ecu (without audible ping, to contradict the above statements), and actually had to go ahead and upgrade the secondaries to stay below 80% duty cycle in a fourth gear run... By calculation, that works out to be much more power than I had expected to get, but the car's owner has not yet scheduled dyno testing or a track run. If and when such an event occurs, and results are as good as fuel-based calculations give, I'll encourage the car's owner to allow me to post the exact set-up.

I think you'd have fun with a wideband for a few hours, 88Integra. You definitely seem to have the know-how to use it, and just not the funds (like everything other student)

88IntegraLS

Lol, a certain upcoming lysholm based project is getting all my summer earnings.

I've got a local friend with a wideband who will be my tuning guide once the usual stuff is take care of (haltech, injectors, etc.)

It appears that the stock S4 NA ecu can be easily maxed on just a mild street port with a header and highflow cat.

pp13bnos

iTrader: (1)

When I had my S5 n/a Rx-7, I pretty much had everything done to it. After everything was said and done, I had Ralph Friend (Groundzero Motorsports) dyno tune it for me. It ended up making peak power at 14.25-1! With my leading timing set at 20 degrees advaced. The car ended up puttind down 167rwhp on a mustang dyno, and trapping 98mph in a full interior, no weight reduction car. (I even had the spare tire in the car. ) The 14.25-1 a/f ratio kinda concerned me, so I talked to Rob@Pineapple Racing about it. He said, making that little power would'nt do and short or long term damage, and not to worry about it. Couple years later, I ended up trading the car in......the motor still ran/started strong as the day it came off the dyno.

I'm shure 88IntegraLS is sick and tired of me talking about my old car. :P

CJ

Nick86

iTrader: (1)

Thanks for all the firsthand knowledge guys!


It's funny though - as this is one of the first times that I have heard of adding fuel up high - pretty much everything I have read has said that you will need to remove fuel from the upper rev range.

That's a perfect example of why I didn't want to just go and plug in the same SAFC numbers as anyone else. Now I have a few AFRs that I can take to the tuner, and we can work on getting the car in tune rather than just "better".



Anyone else have any other tips/advice regarding dyno tuning?


As far as the Vacuum Sensor/S5 TPS options go - would it not be more effective to mount and wire up an S5 TPS under the dash and have it be depressed by the actual throttle pedal? That way it is a mechanical action. My only concern about the vaccuum sensor is that if I develop a vacuum leak , would it not sent an improper throttle reading to the SAFC - and could that potentially be harmful to the engine?

Thanks again guys!

HAILERS

If it's a stock n/a engine, I'll bet you'll be removing fuel. Especially around five grand, not adding it.

Nick86

iTrader: (1)

I'll let you know!

At least I'll know what direction to go if I'm searching for AFRs in the 13 - 14 range.


Any input on the dedicated S5 TPS idea?

Kingofl337

this turned out to be a pretty good thread. Maybe we should move it to the Archives?

88IntegraLS

I know that I had to add some fuel above 4k rpm because my large aux ports probably max out the air flow meter and ecu . .

CJ ur old S5 was tight, too bad I can't race it at the strip! It's amazing that it was one of the most powerful NA's on here but it had only mild porting. I think mild ports are all the stock ecu's can take.

87RX7TII

how bad is it for the seals if you run rich?