Mark_ZZ3

For years I have wanted to dissect a Players PROM. So that will be the purpose with this posting. A bit of history on what GM did or didn't do within the race version of the PROM. I am no expert on PROM tuning, rather trial and error. So as I muck through the R7U prom, I'll post up interesting things.

For today ... It's all about spark! The racing PROMS were designed to maximize the engine output BUT keep the engine from destroying itself. The tuning was made for WOT. Have a look at the two graphs:



The overall spark is similar but there is spark removed in the middle (See dip) and then added to the top. At the top, there is 5 degrees more. In the valley in the middle is as much as 7 degrees pulled out.

My guess is at the RPM change in WOT when up shifting or the precursor to that which is when they are going to WOT. (maybe others can chime in) Rather than wait for the "knock", they removed timing. The valley looks to be 1600-3200 range at about 50% duty.

I know over the years of racing, much of the learned calibrations made it back into production. IF you look at the spark curves in 86-87-88 and up you can see the changes from a basic "mechanical advance" to "all in" ARAP vette style, to the R7U approach.

Mark.
PS. As I get time, I'll dig into other areas. If there is something of particular interest let me know and I can look and post up info.

Mark_ZZ3

Other areas I'm looking at at Volumetric Efficiency and Enrich Power ... both appear to have more significant changes over stock. Stay tuned.

PurelyPMD

iTrader: (3)

Tuning in!

okfoz

LOL

Mark_ZZ3

Ok ... so I find it exciting to dissect the data ... I'm a car geek.

PurelyPMD

iTrader: (3)

I find it interesting as well - Tuning in was just a different way of subscribing.

If you ever get to the point of burning copies, I'd be interested.

okfoz

I am all for it too... I was just laughing at PurleyPMD said "Tuning In" Found it funny because that is what the chip was for, tuning...

I based my tune off of the ARAP...

John

Mark_ZZ3

My new tune (for my son's project) is an 1989 setup, but with the spark curve from the R7U. Going to see how it works. The ARAP seems way aggressive in spark (even with aluminum heads). So maybe GM was on to something with taking the spark out. Not sure ... seems worthy of a try.

I need to borrow a 1989 race PROM and take a read. See what that looks like. Need to ask nicely of a fellow I know a real 1989 R7U still with chip.

Mark.

PurelyPMD

iTrader: (3)

Mark,

Were the proms different on the 1LE cars or just the R7U cars?

Chris

Mark_ZZ3

To the best of my knowledge, 1LE cars got stock proms.

R7U cars had tuned PROMs to promote engine longevity as well as matched for premium gas. shift lights were set at 5100 or so (what GM said was best). While I have not done a quarter mile test between stock and R7U ... the one magazine test that compared a R7U vs. non-R7U showed the R7U was faster in the quarter mile. The PROM was expected to be worth a few tenths. I should find that article and post up ... hmm.

Mark.

PurelyPMD

iTrader: (3)

Thanks - let me know if you decide to burn copies.

92GTA

iTrader: (11)

If you aren't willing to post the .bin file, would you consider a personal "trade of information? I can trade you a copy of my SLP Performance PROM.

I think between the R7U, SLP, and S_AUJP, you could come up with a great base to start tuning from that would give you lots of ideas where to start...

Alex

yaj15

iTrader: (3)

This is a very interesting thread. Would be interesting to see what the performance difference is though testing in car to see what gains the tune gives.

Would be interesting to have a list of what the differences are between the R7U prom and the regular LB9/L98 prom too. Always interesting to see what kind of parameters were changed with this factory GM go fast tune.

TTOP350

iTrader: (8)

I have 2 different SLP chips. Both are 90-92
One is a 305 5speed and the other is a 350 auto
I would like to see the difference from stock they had. (my 89 car went faster w a stock chip and timing/ fuel PSI bumped up over the 89 SLP chip).

92GTA

iTrader: (11)

What sucks is f-bodies didn't get a variation of the aluminum vette heads so with cast iron they have to be WAY conservative due to the shitty heat dissipation but comparison.


But its awesome to see how they did push it and how far.

chevypower91

That is very impressive, Mark.

How do you read this bar graph?

I would think that the proms would be different for the R7U cars as they would need to be calibrated to match the mods completed to the motor.

My '91 is a 5.0 / 5 speed car and i'm not sure if i have the stock chip or aftermarket. There is no sticker (as I have seen on other threads) on the prom itself to identify it. Is there a way of doing so?

Mark_ZZ3

Here is another pic:

Top is R7U. Middle is 1989. Bottom is my hack one.

You will see the big valley in the R7U one which I interpret is where the RPM drops when shifting gears. Rather than let it ping and retard timing, they removed it. No ping.

Well my uneducated guess.

90 GTA Black

Put me down for a copy of the Player's prom as well.

Mark_ZZ3

The only reason I don't post it up in full is that there are those that will take it and "sell" it. I guess I really don't care ... but I never collected this stuff with intentions on making money. Just fun and interesting stuff.

So I would share with those who want it for their own person interest. Not for profit. Ideally ... someone like me who will compare and discuss what they find. I think we will all will appreciate knowing what GM choose to do in the PROM.

Cheers!
Mark.

Mark_ZZ3

If you want to assist with the decode ... please drop me a PM with your contact details!

Mark.

TTOP350

iTrader: (8)

I'm just wondering, if the tuning had anything to do with the different exhaust used?

67restoproj

Where is the PROM located?

Mark_ZZ3

I'd assume your car will have one still in it. Many 91's still had them as they were raced in 1991 and in 1992. Have a look. If not, I could help you make one.

67restoproj

Where do I find it?

Mark_ZZ3

Pull down the ECM (Passenger side behind dash access from bottom - remove panel). Open door on ECM (held on with two bolts). Look in round window of the blue PROM PAC. If it is stock, it will have a sticker viewable through the round opening ... usually with two rows of numbers/letters. Race PROMS had no part number, but had the special yellow engine seal paint on top of the PROM.

I can post a pic of a RACE one if you need to see.



Mark.

Jaysz28

iTrader: (30)

Did the RU7 cars not have emissions (cat, AIR, etc)? If not, then that could account for the difference in the spark table

Mark_ZZ3

Cats were bypassed with open exhaust.
Teams could remove the smog pump in early years. Unsure about the Serpentine setup. I can't recall reading that.

So yes ... less emissions.