Kerry Chadderton

First off, I've searched here, Google & Pelican. I have a specific area I want to change and wonder if there is a way.

I have a mostly stock engine 84 N/A set up for the track. I rarely drive it on the street other than testing or driving to the track. The car is very well sorted. The only modifications to the engine are:

Catless exhaust to a Flowmaster
1986 AFM & DME
4 degree cam key
Aftermarket throttle cam
Wide band AFR (Zeitronix)

Seriously, that's it! Everything else in the engine compartment is "as delivered"

The entire fuel system has been removed, tested and/or replaced. New injectors, fuel pump, fuel filter, FPR, Throttle body rebuilt, new DME temp sensor, new DME relay.

I want to change one operating parameter: WOT AFR

The engine runs very well. AFR is normal throughout the warm up time period, and during operating temperature under normal driving. However, at WOT near the top of the RPM range (5200 to 6200) the AFR gets into the 12:1 to 11:1 range consistently. This happens with the original 1984 AFM/DME as well. The engine power goes flat at the same time. I can't help but think there would be more power available if the AFR was closer to 13:1 or 14:1.

Is there a way to adjust this?

wildcat077

You would probably get better AFR results if you installed an aftermarket chip in your DME.
I switched from a stock early 83 DME and AFM to an 86 DME and AFM and I tried a various number of chips and I got decent results ...
Seems you are running very rich ... in my case I had to richen the mixture considerably with a Lindsey adjustable FPR as my engine was starving for fuel ... without posting any HP numbers I will say that my engine was tuned on the dyno to run at 13.7 AFR at WOT with a stock cam and head !
You most likely don't need that timing key either to achieve better results ...

First thing for you to do would be to get your car on a dyno and play with the fuel settings on the DME,it's hard to dial in correctly without the use of a dyno ...

My car is an 83 SP2 race car.

Cheers
Phil

Kerry Chadderton

Phil,

Thanks a great deal for the response. I understand and agree. Unfortunately I don't have a dyno or support group within 2 hours drive time.

I was seeing 13.8ish WOT with the same 84 DME/AFR and stock cam key. The world was fine. I wanted to get a little more mid-range coming out of turns so I switched to the 86 DME/AFM, 4 degree key. Then I was seeing as rich as 10.3 WOT. Lap times were horrendous and, hell, you could feel it fall off up high (5100-6200). I switched back to the 84 DME/AFM and still got 11 to 12 per my original post.

I assumed it was a FPR issue. I did every test known to man, Clarks and FSM. Everything passed. I got desperate and threw parts at her anyway. FP and FPR were 20 years old. What the hey, its only money.

It just pisses me off. I'll do that rebuild in the winter and tune after that. Too rich is safer than too lean.

kevin12973

You can adjust the spring pressure on the flap inside the AFM. Less pressure=more fuel. I will not elaborate, just search "adjust AFM" and read the thread. Caution- there is an AFM expert that insists its a bad idea to tune like this but seems people have had success. This will change afr across the board however but not a big deal for racing. I caution afr's over 13.0 wot, is to lean and looking for a melt down. Cruise 14.7 is ideal, but not under a load. Be carful and good luck.
Regarding the 4 deg offset key, I thought that helped lower/mid rpm power while sacrificing top end hp. The opposite you would want for the track. Did you use it to advance or retard cam timing?

Noahs944

Try adjusting your ecm. 7 clicks of adjustment. On late model ecms anyway. http://www.motronic.ws/fqs.htm

Rogue_Ant

I made tools for tuning the stock car years ago, and put them up for free:

http://www.roguetuning.com/diy_free_944_tuning_tools

tempest411

Am I correct is thinking your MAF conversion has been unavailable for quite a while?

fejjj

Saw this other post and thought it might be helpful.

http://https://rennlist.com/forums/924-931-944-951-968-forum/864066-interesting-afm-tuning-procedure.html

konakat

The throttle position sensor (TPS) senses wide-open throttle and tells the DME to ignore fuel maps and just dump fuel as much as possible. You can try disconnecting the TPS so the DME always uses the main set of maps, both at idle and WOT.

Tiger03447

Re: The rogue tuning post: does this mean that Joshua is back in the DME game, or is this just wishful thinking on my part?? Thanks, Tiger 03447

Otto Mechanic

Joshua, would you happen to know where I could get more information on the DME mods made for the '91 Firehawk S2 cars? I expect there were quite a few variations but if you have any pointers to people or articles on the types of things done to those cars I'd appreciate it.

Thanks,
Otto.

divil

I don't think this is quite right - at least in the case of the 951, there is another fuel map for WOT, and I imagine it's the same for the NA. It's a simpler fuel map in that it only takes RPM into account, and just assumes full load...but I don't think that's the same thing as just dumping as much fuel as possible in there.

konakat

Fair enough, that would make more sense. Either way, if you were always using that map you would run rich all the time.

Rogue_Ant

Yes, I pulled it when my Son was born (Sep '14).
I've been working with Lindsey Racing, as they are taking over the day-to-day operations of my kits.
That said, I should have the NA-Tune back up for order here shortly.

Absolutely not correct.
The DME will use the WOT fuel map, and fuel according to its target AFR (which is richer than the idle & part-throttle maps).

Working on it. Things are starting to settle a bit for me.

I don't know much about the Firehawk S2... They had a higher rev-limit, and other tuning changes (DME software). But its been years since I looked at it, and I just skimmed it again, but it would take a little while for me to do a proper comparison.

Noahs944

Joshua,

-Good news to hear you'll be producing N tune kits in the future. Should, woulda, coulda.

-I just checked out your TunerPro freeware to tune our 944s. Amazing! That's what I need. THANK YOU. (2 questions: do you know if it'll work with XP?). Also the FAQ link regarding tunerPro doesn't work. It would seem as though this Tuner Pro might also be what Kerry C needs.

Keep up the great work.