Awesome, thanks Howard!

I have gauges for fuel press and some others, but it never crossed my mind to datalog them.

My EGTs go very hot at the top of a run.... 1825ºF OR 1000ºC. It scares me to death!

I have tried mediating the temps with 50/50 Meth and 100% water, have also tried advancing and retarding the ignition with very little improvement if any.

This is what a logged run looks like on datalogit. It is hard to make out the pink and yellow traces of the EGT. Sorry.

This time extra knowledge is frightening! Any ideas?

Barry

http://i287.photobucket.com/albums/l...bordes/egt.jpg

Only thing I can offer for your question barry is support that I also have very high EGT's in the upper RPM ranges :)

I can crest around 975C by redline (8000rpm on my FC block) at 20psi (T04-R, 67mm compressor.....1.00a/r divided rear)

I've also tried a number of different things to reduce the temps, but I'm starting to think that perhaps back pressure is the real culprit for the high temps...unfortunately I do not yet have this parameter monitored in my car :(

The largest difference between my car, yours, and howards, is the fact that he has nearly DOUBLE the turbine area, and exhaust area and volume we do. And his EGT's are reportedly solid and *much* lower then what you and I have found.

Classicauto, which manifold are you using. Didn't you switch from a cast to a tube type? If so, did the temps drop lower assuming slightly lower backpressure?

Maybe a 4" downpipe would also help drop backpressure.

I am using a RB 3" single tip catback. People speculate on these having high backpressure.

Barry

Barry, yes I moved from an FC greddy cast (collected, an majorly unequal runner length) to a-spec's FC manifold. It would be considered medium length IMO. Runners fully divided, length about 9".

The EGT's have gotten slightly lower on the setup. A decent back to back test was on the very same engine (basically stock port S5 TII) done minus the turbo change....

Using the cast with the aspec GT3574 .84 T4 housing, and same WI nozzle, EGT's could touch just over 1000C by redline. (@20psi)

Aspec manifold, T04-R 1.00 T4 housing and same WI nozzle, EGT's stay under 1000C (usually 975C highest) by redline.(@20psi) (also note, that this setup with larger turbine housing and turbo was as responsive as the old on the log type mani!!)

They have also stayed more equal during boost between front and rear with the new mani.

Exhaust on both setups was custom 3" piping from turbo splitting to dual 3" infront of the axle.

I've also thought of moving to 4" from the turbo down to the 3" split. Turblown has told me the extra volume is really helpful on a p-trim turbine (what my t04-R has)

I doubt I'll make that change this year though, because I'd like to be able to log EBP, and make the change on the dyno for a direct comparison.

Classic,
It would be interesting to see your temps with larger AR turbine housings, say .96, 1.0, and 1.15.

I really think that our high EGT are a port overlap problem. The exhaust gases are contaminating the incoming charge causing a slower burn rate.

The solution then might be to redesign the exhaust port to slow gas reversion.

Barry

Interesting thought!

Whats your port configuration barry? The engine I ran on the two setups outlined above is a stock port...for the most part. I cleaned up some casting and added a little shape to the bowl, and brought the intakes UP ~2mm on primary and secondary.
Exhaust was slightly widened, and brought DOWN ~2mm.

Stock overlap (S5 TII block)

Also, on your point of running different size turbine housings, note that I did step up from .84 on the old turbo to 1.00 on the T04-R :)

EDIT: That stock port engine is currrently being "refreshed" and I'm thinking of going a little larger all around on the exhaust to promote better evacuation of those hot gases, thoughts on that?

Oops, I missed the change to 1.0 from .86 on the turbine housing. I would have thought that going larger on the AR and dropping the cast manifold would have dropped the EGTs more.

My ports are from a Judge ITO template.

My thought on the exhaust port is to smooth the bottom and sides for more flow but on the upper/closing side to duplicate the stock Mazda sharp step and possibly adding a second step at the beginning of the sleeve to help discourage reversion.

If you notice F1 headers (and others) use reversion cones every few inches on the exhaust headers. An idea we need to incorporate.

Barry

Hmm, you're good at turning the hamster wheel in my head barry.

Most of what I know about anti reversion sleeves or chambers is in regards to non turbo exhausts and design. Do you have any information about how it relates (or if it even differs) to a turbo application?

The simplest design which I would think fairly easy to include in a mani. would be these:

http://www.patentgenius.com/image/6336471-3.html

I'd imagine them directly placed on manifold flange?

Also, on the A/R change I made, the only other variable that I can think which would have made the change have less impact on EGT's would be because the .84 was on the aspec tubo which uses a - according to aspec - more rotary suited (larger I guess) wheel from the GT line, where as the t04-R has the trusty, but very old design, p-trim.

But I'd hope for a greater decrease as well :(

From the TCS sensors website mentioned on page 1:

"Analog Retransmission Output: User Selectable; 4 to 20 mA, 0 to 20 mA (1 to 5 VDC or 0 to 5 VDC using included 250 ohm resistor)"