I've been wondering about this...
I thought about this for awhile (bad idea i know) on my last trip home. While highway cruising at like 75 or so (~3200 rpm) i notice my EGTs tend to be rather high (700C with probe in downpipe), and this only gets worse as I get on the boost, like when climbing a hill or something. I've had the EGTs creep up to ~780C during one of the longer hillclimbs. Now, I assumed that the higher EGTs during straight cruising are due to closed loop mode running far closer to stioch than the ECU does under load, but what about during the climb? I am right below the secondary injector engagement point, so I figure that I could be running dangerously high DCs on the primary. I guess I'm just looking for some input from the forum gods on this soley to increase my knowledge of how the system works, and whether or not this is a problem (which I kinda assume it isn't otherwise people would blow their engines all the time on hillclimbs).

S5 TII, ported WG, 3" turbo back and TID, stock injectors, no fuel controller (yet)

thanks for any input

 

So buy or borrow a DMM that can measure frequency and duty cycle and find out for yourself. It's easy to do and beats the guesses you'll get here.

 

^ that's a good plan

speculating though, I doubt your primaries are being overworked unless they are dirty. I know guys who push 250+ through stock primaries with 720 secondarys.

 

The other possibility for a sharp rise in EGTs under hard acceleration is that it is running so rich the extra fuel is burning in the turbo and that will jack up EGTs.

What AFRs are you running?

James

 

What kinda boost are we talking about here?
How long are you in boost for the EGT's to hit 780C?

700C at closed loop at under 4kRPM is actually kinda cold...


-Ted

 

why would you think that 20 year old stock injectors are dirty?



hahah just kidding but yes you would be amazed at how much better these cars run with a new set of injectors.

 

Stock boost, about .5kg/cm. I was just taking things from you site Ted where it says EGTs in the downpipe are safe at 700C.

Injectors were cleaned last summer by Cruzinperformance. I wish I had a wideband to further monitor this, but college and modificatiosn don't go together well.

 

EGT's do creep if you keep on the pedal long enough.

To give you an idea...
I was doing 14psi for about 20 seconds.
Yes, the car was going over 120mpg at the time.
The EGT's normally would sit around 720C, but under that prolonged WOT it was creeping PAST 900C!

On a 1/4-mile drag pass, my engine was happy at 720C with the probe in the downpipe.
On closed-loop, it would hover around 760C.
This is with the stock FMIC too.
Higher EGT's were (probably) due to heatsoak of the IC.


-Ted

 

But you really should put this in context.

Ted where was the sensor?

JDMsuper7 where is your sensor?

James

 

I'm really, really interested in how you get 120mpg. Maybe just give me half your secret formula. Sixty mpg will do me fine.

 

Racing Beat 3" downpipe, right at the flange...

I think he / she mentions it's in the downpipe also.


-Ted

 

Aw crap, that was supposed to be "MPH" not "MPG". :P


-Ted

 

My probe is about 2-3" down from the turbo in the 3" downpipe.

About this creep... is it actually the engine leaning out? Or is it just because everything else (downpipe itself esp) is warming up due to the increased heat?

 

No, it is not the engine leaning out.
In my case, it's the IC getting heat soaked.
Well, in fact, EVERYTHING gets hot.

This is where an efficient (front-mount) intercooler will help you significantly.


-Ted

 

Thanks ted, I was really curious about this. Front mount isn't in the budget right now, but that is some good information.

-Nick