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PORSCHEV · Posted: Fri Jun 06, 2008 10:13 pm Post subject: Timing Advance?? and 2008 update

I am running the euro pistons with 9.3:1 CR as well as a piper cam. I can't recall the specs ATM for the cam. I may have to email andrew in NZ for them.

I just installed the cam yesterday and I set the timing at 12 degrees advance. The car seems to pull ok after 3000 rpms. I ran the car 50 laps or so with a stock cam with 10 degrees advance prior to installing the cam to get a feel of how the engine would feel.The cam didn't make a huge difference compared to the pistons and refreshed engine.

It amazing how much work you have to put into your car to make it fractionally faster!! I estimate that I am running 25 more hp and 35 more ft of torque. I also have 15" goodyear slicks with an 8" footprint that really grab the track. I worked with the car on set-up to the point I can take turns 3-4 at 90 km and let go of the wheel and the car will take the corner by itself

Last year the car at best ran a lap time of 20.6. This year I am just breaking into the 19.9 range. SO....thats alot of time and money for 7/10th!!!

My local track is going through some major growing pains where the 4 cyl modified class has folded due to lack of cars. I had the option of going back down to the 4 stock class where the cry and whine that my car is unfair even tho it's meets the rule criteria. I also had the option of running with the 6 cyl modified class. They mostly run sportsman chassis with a mild modified engine. So rather then slowing down I opted to take on the big boys. The best lap time I have seen in that class has been a 19.5..so I am not too far off the pace. Bit nervous running a 2000 lb car with 3000lb cars......but what the hell!

Almost forgot. The best mod I made for the car was the GT nose panel where I made duct work to the rad from the 4 upper openings. I ran the car HARD for 20 laps and last year I would be running 3/4 on the temp gauge..this year I can't get it off the 1/4 mark!! Awsome improvement!
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1976 924
5 lug conversion, 17'C2 wheels,custom body work,327 vette engine.

1978-#53 "D" track racer.

RC · Joined: 25 Mar 2007 Posts: 2637 Location: Australia

Good effort really Porschev.
7/10th second is a definite improvement and will cover a lot of track in that time. But yea, its expensive and more difficult to gain those extra 1/10ths.

Unsure what fuel your`e running but in my experience you could run over 15 initial safely on 95 or higher with a Euro dizzy. Especially with a longer duration cam timing advance will yield much improvement. Conservatively try advancing a few degrees at a time until the onset of pinging (on a hot engine and even with slightly lower octane fuel) then back off a few degrees.

Best of luck this season.

Roger

PORSCHEV · Posted: Sat Jun 07, 2008 2:20 am Post subject:

That was my next question. I am running the north American version of the dizzy. Do I need to swap in the euro to the get the proper advance curve?
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1976 924
5 lug conversion, 17'C2 wheels,custom body work,327 vette engine.

1978-#53 "D" track racer.

RC · Joined: 25 Mar 2007 Posts: 2637 Location: Australia

PORSCHEV · Posted: Sat Jun 07, 2008 11:24 am Post subject:

Man do I owe you a cold beer for that response! Well written! I will do exactly what you said and let you know the results.
_________________
1976 924
5 lug conversion, 17'C2 wheels,custom body work,327 vette engine.

1978-#53 "D" track racer.

endwrench · Joined: 07 Dec 2002 Posts: 1631 Location: Victor, Montana

Great response by RC! I would only ask if your RPM ever falls below 4600? The ROW 110HP curve isn't all in till that point and the Euro unit is all in by 3500rpm. And for some reason, according to the graphs in Haynes, the ROW units taper off about 2° at 6500rpm after peaking at 4600rpm. The Euro units do not do this. Not a big deal but if your looking for every advantage.....

Todd
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'79 924NA. Rebuilt 9.5:1, MSDS header, Mega Squirt Injection, MJLJ-EDIS Ignition, 1.6L Whipple Charger and Intercooler, 10lbs Boost, 944 Trans, Custom HD Clutch.
"simsport" said....superchargers are better than turbos its official!....

PORSCHEV · Posted: Sun Jun 08, 2008 8:53 pm Post subject:

I set the timing at idle to 16 degrees advance and then spun it up to 3500 rpm...I found the total advance at that rpm was 33-35. This makes more sense now with what your saying endwrench.

I do need the rpm's below 4500..lol When I exit corners 1-2 I am around 34-3600 rpm. Down the back stretch I peak out at 6200+.

It will have to be what it is for today...it's the first race day of the season

_________________
1976 924
5 lug conversion, 17'C2 wheels,custom body work,327 vette engine.

1978-#53 "D" track racer.

RC · Joined: 25 Mar 2007 Posts: 2637 Location: Australia

Well how did you go?
Hope ya kicked ass

Just had another look at those advance tables while posting my EFI settings in another thread. Endwrench is right with the 4600 RPM for max adv on the 110Hp dizzy. Think I must have counted 200 RPM per square to get 5200. Anyway even at 4600 it comes in too late, even for a hot cam. IIRC Piper only have 1 924 grind that is "fast street, or rally", not super hot.

Unsure why the US dizzys retard that 2 deg after the peak. Possibly as a fudge factor against the CIS leaning out with lower fuel? emissions?

So if youre after those 1/10ths look around for a Euro dizzy, or go programmable. Could likely go with a little more advance on the current dizzy but check it at > 4600 as its still climbing at 3500.

Roger

PORSCHEV · Posted: Tue Jun 10, 2008 11:13 am Post subject:

Well the timing couldn't have been to bang on for me race day. My class got thrown in with the stock 4's again this year

and they were pulling along and some were out pulling me on the starts. NOT COOL.

The car was alot faster in the corners but that was all to do with set-up and great tires. I didn't take any checkers this week, but that was due to the fact they started the modified cars behind the street class and made us work our way through the field...but you can't pass when they are 4 wide!

Back to the power issue I am starting to think I should really look at having the injectors serviced since they didn't have the best spray pattern last I checked and going over the ignition.

During the feature race I was running strong out front when the right front hub of the rotor decided to shatter. Luckily I felt it go "funny" and pitted right away. I wonder if there are any better then stock versions out there?
_________________
1976 924
5 lug conversion, 17'C2 wheels,custom body work,327 vette engine.

1978-#53 "D" track racer.

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

I know I have seen an aftermarket hub online, I just couldn't find it. The ad says, "Don't let a failed hub ruin your race weekend. SCCA legal."

I'll check back if I turn up the site. . .it was for a 944.
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Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

924RACR · Posted: Tue Jun 10, 2008 10:25 pm Post subject:

RC's dead-nuts on. We run ours with 42deg total advance, no vacuum connections at all (centrifugal only). Tried pinning them once, didn't work. 9.5:1 CR with 93 octane pump gas, and a 4 deg cam key. In our case, this works out to about 12 deg base timing at idle (stock US distributors).

I highly recommend actually checking it revving the engine up to speed; your advance may not be performing as you expect, and you'd hate to find out the hard way by blowing a motor.

I've seen that hub too. Not SCCA legal across the board, but a good replacement. OTOH, I've never had any issue with stock hubs, yours must've been bad. Magnaflux is the best way to go...

HTH...
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype