Oddjob

Anyone seeing 1400F or less EGTs under full boost loading?

Spoke to a local p-car raceshop owner/builder, and he said I should adjust the fuel and timing to get no more than 1400 on a dedicated track/race car (otherwise the motors wont last long - headgaskets, burned valves, etc).

Im used to hearing around 1500-1600, but he said that is too hot. He would prefer to see 1300, but may have difficulty getting that low on a turbo.

Not a high boost application, somewhere between 13-14psi peak.

Assuming that 1400 is possible (and if I assume that it is necessary to run that cool) - what would it take with A/F and timing to get there?

Perry 951

I don't recall anyone posting of temps below 1400F under full load, stock or modified. I don't think 1300F is possible with a good tune.

Under 1300F is not likely to happen unless the temp probe fell out, the tune was excessively rich, or if the timing was so retarded that most of the combustion happened in the headers and crossover.

Oddjob

Yeah, I dont recall seeing anyone ever posting EGT results that low either.

Im not even sure how rich and how much timing may need to be pulled, just to get into the 1400s.

toddk911

I've always been told try to stay in the 1500-1550 range.

Well, pulling out a lot of timing will increase your egt not decrease.

RKD in OKC

Mine were always in the 1500 to 1600 F range. No burnt valves or anything on the rebuild after 10,000 miles with those kind of temps.

azmi951

same here, 1550-1600 under full load. Hotter with the old weltmeister chips.

hosrom_951

Dedicated track car means running high octane fuel, thus having timing advanced, or more advanced than pump fuel, thus less EGT's.

Timing effects power, torque, detonation and EGT's and is related to how much boost you run. No matter how safe or solid the AFR is, one would need to adjust timing.

We all know how to adjust AFR, it's pretty straight forward, the sad part is, due to the nature of having very competitive vendor's/people in the 944 field, timing maps and exact explanation of adjustment (tables and so on) is not usually shared.

I mean, most of us know what advanced or retard timing is, but what exactly do the values in the table mean and how to set/adjust them right is a big secret.

toddk911

Good points Hos!

So are stock timing tables even public info??

hp18racer

Mine peaks and holds at around 1650 on the track on a long straight. On the street I don't often see over 1550, but it is still climbing when I run out of speed limit or the desire to exceed it.

Stock #'s are in the picture, Autothority stage 3 timing, intending 93 octane...
1000 70
1480 70
2000 65
2120 63
2240 61
2520 58
3000 56
3280 55
3520 52
4000 52
4520 54
5000 55
5520 56
5800 57
6000 58

I'm running mostly 9 ticks higher numbers than autothority on 100 octane in the range where I'm on boost.

ibkevin

...

Oddjob

Quick background: with the venue/class rules that I race under, I need to run the factory bits and pieces; so factory boost system, factory ignition system, fuel system, etc. So no adjustable FPR, no programmable ignition, no adjustable boost system. The boost limit for my particular classed car will be limited to 1bar (approx 14.5 psi) max. There is some limited ability to change the boost levels to match fuel delivery (although its an ***-backwards way of doing it), and also some ability to change ignition and fuel (see discussion below), but in general I do not have a lot freedom in tuning the car.


This is all part of my question: does retarding the timing increase or decrease EGTs. Theoretically it can do either, depending on where you are on the curves. And I don’t know where we are on those curves.

So, with stock chips running pump premium, and using the FQS to retard the timing by 3 deg (-2.73 I recall?), will that increase or decrease EGTs? Then what about combining that with +3%, or +6% fuel? EGTs go up or down?

Leading to this: I am looking at running factory motorsport Escort/Cup chips, which have some timing advance over the stock chips. I am not certain I want to run these, since the Factory stated to use 104 octane, which I wont have ready access to (100 at best).

I am trying to find out if these factory race chips have the same Pot/FQS settings as the stock chips (I have a separate post on this, but it has gone unanswered). If the FQS settings are the same, I will have the ability slightly retard the timing (which may be necessary w/o 104 octane) and increase fuel at increments (3-6%) and go to a 3.0 bar FPR (allowed within the rules, since the Escort cars used the 3.0 bar FPR) to get even more fuel as needed.

At this point, I do have a wideband and an EGT, so I will do some testing, but I just wanted to look for some ideas on what to expect and where to start. I was discussing this with the local p-shop owner (has a national reputation within Club Racing cirlces for building extremely competitive stock class 944 series motors). I commented on expecting 1500-1600 EGTs, and he stated to try to stay around 1400, lower if possible and no higher than 1450. His recommendation to drop EGTs, was to add fuel and use the FQS to retard timing.

RKD in OKC

Your mechanics recommendations sound great for a NON-TURBO car.

Oddjob

Yep, and thats why I clarified it, to ensure he was referring to Turbos. Said he runs the S2s at 1300....

Laust Pedersen

If you want to make you mechanic happy, just measure the EGT after the turbo. In the X-over pipe you may at 1 bar boost have an average of about 1.5 bar over-pressure. If you pressurize a 1300F gas to that level you’ll likely end up with a gas in the +1600 F range. If you assume an adiabatic compression of an “ideal gas”, that can be calculated.

The question of EGT vs. AFR is a little tricky. For the same power produced, stoichiometric AFR gives the highest EGT, however extra fuel cools down the intake air, therefore more power (until an AFR of about 12) and therefore more heat (calories per combustion) is produced. Overly rich though, both the power and EGT will drop.

Hp18 racer, showing a virtually uncommented timing table like that, leaves the impression that the numbers are in degrees relative to TDC.

Russell’s (rberry951) MaxTune (http://www.maxhpkit.com/) demo is quite informative on timing and fuel maps. It can also show timing degrees based on raw numbers.

Laust

Oddjob

Only trying to make myself happy. The shop owner would probably be happy if I burned up the motor and gave him a blank check to fix...

And the location of the EGT was discussed as the test port on the x-over pipe, since I will be using your EGT kit. He also prefers using the test port vs installing in the individual headers.

I believe his intent/recommendation was to run pretty rich, at the expense of a few hp.