OZ951

Seems like a few guys are running with EGT kits now, so I am curious as to what sort of readings your getting in normal driving and at the track. I'm particularly interested in readings that are correlated with an accurate AFR and ignition advance. This kind of info should be handy for identifying minimum advance at peak torque as well as being good background info for typical numbers for 951s.

toddk911

At full boost, wot you want to stay around and/or under 1,500-1,500.

reno808

ST is your man on this one for Sure

Chris White

The problem with running a modified turbo on street gas is that you will have to be conservative enough on the timing to avoid detonation that you will run the EGTs up. I have seen up to 1700+ on the track – but the engine will still hold together at that temp.
Run some higher octane and you can add some timing and drop the EGTs.

OZ951

Thanks Chris,

I am hoping that the local M102 (102 RON 90 MON) will be good for 24-25 degrees after peak torque with a reasonable EGT and not overly rich AFR. In your experience have you seen much evidence of burned valves in 951s?

toddk911

But that is only a situation of A LOT of boost...20-25psi+

But brings up a question Chris. What kind of EGT's can a motor handle in a street situation? I.e. brief bursts???

333pg333

Wayne, are you saying that our 102 only equal the US of 90? I know we're behind on the octane ratings but I didn't think by that much. So our premium Pump that is 98 or 100 w 5% ethanol is less than 90 U.S.? Maybe I've misunderstood.

Rogue_Ant

US uses (R+M)/2

So your local M102 would be a 96 octain rating here in the US.



Rogue

OZ951

Correct. Patrick, the race gas should also be more consistent in its quality on a batch to batch basis than pump gas.

RolexNJ

Here is an easy solution or additive, use xylene as extra insurance.

Chris White

The 951 is very hardy when it comes to high EGTs. The down side is just more long term stress from heat cycling the headers, wastegate and the rest of the exhaust side parts.
If you have carbon build up you can risk burning an exhaust valve. It only takes a split second to burn a valve if it is held off the seat during a combustion cycle at high EGT (Yes, I have one of those!).
On the street? – not an issue (unless you are getting insanely high EGTs) keep in mind that on the street you may see some high temps but the flow rate is much lower. In fact some of the highest temps are during the warm up period (ignition is a little more retarded when cold)

mikjel

I checked the afr and egt (using an autometer pyrometer) on my COMPLETELY STOCK 951S before I did any modifications to it..

I saw 1650+ Fahrenheit at wot at 6000 rpm, boost 10 psi (falling from 12).
Afr: 12,7:1. Egt-probe ca 1 inch from the head on cyl. 4.

I also saw 1650 Fahrenheit at 6000 rpm cruising (no boost), afr: 14,7:1

hp18racer

My car tops out at under 1650 on the track , Afr just under 12:1. Very hard to get it over 1550 on the street.

OZ951

Mikjel, that info about the stock EGTs is a good data point... higher than I would have expected but no doubt it was a factor in Porsche's original choice of valve/seat/port design and timing.

Chris, thanks for sharing your experience regards damage you have observed.. I wouldnt have thought that a valve would burn quite as fast as you highlighted..... I wonder what Del West charge for their titanium valves?

Thanks hp18racer for your input also

Rogue_Ant

I would like more fuel then 12.7:1 under full-load.



Rogue