Old Slow Coach

Hey guys, I'm wondering why so often in discussions about dyno pulls, people comment on their a/f (for obvious reasons), but so very rarely comment on what their max EGTs are. I'm relatively new to the game, but have had the impression that this can be extremely insightful and helpful data. I can imagine many situations were someone might not have the best flowing exhaust and is making big power numbers, and has fairly conservative a/fs, but has pretty high EGTs. I'd be hesitant to congratulate someone who has high power numbers AND high EGTs. Is it not true that high EGT will shorten your engine life and can be a contributing factor to knock? Maybe there is a reason for it, but I'm wondering why so little EGT reporting occurs. WTF?

88fc3sw/HX83

1600 - 1650 max IMHO

RETed

Go ask max about it since he seems to be telling everyone what they should be looking for...


-Ted

Maxthe7man

Try the 700 c Ted suggests, I look forward to your future post of black smoke and a flaming bumper....

Old Slow Coach

It appears there was some prior discussion between you guys; I don't know anything about that.

You know, 700c at the header is not the same as 700c at the tailpipe. My EGTs are picked up at the header. Do most people pick them up before or after the turbo? Say you have 875c at the ports, what would one expect at the DP, MP, TP??? (Assume no emissions control equip)

Old Slow Coach

On a highway 4th gear pull, at 22lbs boost, with 11:1 a/fs, my max EGTs (picked up at the header) are about 875c.

Maxthe7man

Best place is tapping the inlet of the turbine housing.. From every system I have seen tuned using EGT's as a tuning reference, that is where it was tapped, even by as many as 5 different rotary tuning shops..
You have to use a pretty stout probe though, if it breaks off it will go through the turbo, but pre turbo, response is much faster.. Keep in mind the driving force of a turbine is heat, post turbo will reflect readings lower that what it actually is..
I have been using a industrial grade 1/4 sensor with good reliabity with a industrial guage that is much faster than the automotive egt guages... Got it for free amazingly..
The other thing I think is part of the reasoning for installing it in the turbo housing, is that the fitting doesnt seize in very bad like it does on stainless headers and downpipes.. The fitting that came with my thermocouple was stainless 1/4 npt swaglock... Stainless on stainless +heat pretty much equals trouble when trying to get it out...
Got to SDSEFI and read their tech articles on egt, its some of the best info out there...
I aimed for mid 900's and thats where I make the most power pre turbo and what was given to me as the best range by alot of Japanese tuners I met over the last 2 years, and is backed up by numerous tuning articles in Hyperrev and the Japanese Rx-7 magazine..max

Maxthe7man

The other night coming home similar run , I took the car up to 20 psi in 5th , egts levelled off at 940 ish , intake air was about 40 deg F, Af's were 11-11.2...

Old Slow Coach

Max, that's great, helpful info! Thanks!! I've got a 3.5" exhaust. Say, what size exhaust you have? Also, would you expect to see difference in EGTs between a 3" and a 4" exhaust set-up. If so, could you speculate on how big the diff might be? If you see 900c on a 4" exhaust, what might you expect it to be on a 3"system? Would it be 900c, 915c, 950, 1000 on a 3" system???

Maxthe7man

I am not to sure to be honest, I will be able to tell you in a short while, I am moving up to a 4"x dual 3" system pretty soon... At peak power I think my exhaust is currently restrictive with a T51, Although after seeing cars tuned with some pretty massive exhaust systems, the egt didnt really wander much off those numbers, and the turbo size really didnt change the egts that much either IIRC... It just seemed that when cars were tuned to a safe peak torque on pump gas, they all ended up in that egt ballpark... Not sure if size would change that much, but I would think egt response time probably would...
here;'s the exact link for the sds:
http://www.sdsefi.com/techegt.htm

Howard Coleman

iTrader: (6)

i try not to miss an opportunity to promote egt usage while tuning.

i use two Teamrip.com K thermocouples each situated approx 1.5 inches from the exhaust port flange. they output to a small circuitboard box with two Analog Devices AD595 chips that convert the millivolt signal into 0 to 10 volts. i then divide the 0 to 10 to 0 to 5 volts and run it thru my datalogit. so i get an Exact EGT in each of 400 cells complete w maximum and minimum. in addition i can strip chart my front and rear egts and relate them to afrs, tps, fuel pressure (which i log).... you name it.

recently i hooked up two Greddy EXT analog egt gauges, i hooked up both my 5 and 10 volt outputs to 4 digital multimeters and also ran them thru my laptop to read both volts and temperatures. i then set up my video camera and went for a drive.

after extracting all the data and posting to an excel spreadsheet i constructed line charts and then attempted to draw some conclusions...

anybody want two Greddy EXT gauges? seriously, i will part w them for postage as they are useless compared to digital.

secondly, i found my Jeff Feltman-designed (Jeff48) circuit box to be dead on.

i have found that as you get down to one bar boost you can have great afrs but 1800-1900 egts and that one or two degrees of lead timing will get you back to 1750 to 1640 where you need to be. you will never pick that up on a cell by cell basis w an analog gauge.

and it is essential... there's lots of blown motors out there that if properly instrumented would still be running.

serious rotory guys will spend some time this winter acquiring the teamrip (absolutely instantaneous) thermocouples ($45 per) and build themselves (or have some geek friend build it) a circuitbox (cost is almost zilch).

you need to know your egts at the port on a cell by cell basis.

the circuit is on the forum search Jeff48's posts. thanks to Jeff Feltman for a dead accurate tuning device that is essential.

howard coleman

Old Slow Coach

Sounds like great idea to monitor both cells! With this, you can pick up problems per rotor early that you otherwise may not find until much later.

Maxthe7man

Howard you are right about the needle egt guages...I never saw anyone use those things for actual tuning on the dyno, although everycar pretty much had one, Japanese like their bling bling to... Mine to is a digital reading guage.
Every tuner used their own trusted instruments that were known to be good and accurate... The guages in the car were checked against the tuners own instruments for reference, but those are there for driver warning, not pinpoint setting of the tune of the motor, as you said, they don't respond well enough.. If the cars egt read basically 1700 all the time under boost, then one day rocketed to 1900, its just enough to let the driver know to have the tune/car checked, or something has gone wrong with the guage..
I have redundent guages for pretty much everything in my car, I check all my pressure guages against instrumentation guages on pretty regualr basis to look for inaccuracy and guage faults...
The worst is the auto meter boost guage, its boost readings are very inconsistant...

Old Slow Coach

EGTs are important and provide valuable insights into the mechanical and tuning aspects of one's set-up, so when someone starts a thread on their dyno results, why do folks more commonly report on the weather conditions on the day of tuning/dyno pull than they do the specifics of their EGTs?

Maxthe7man

yeah Howards pretty hardcore, its a very good idea though...
I have been shopping for a new ems and am looking for one that will log dual egt's for that reason...

Maxthe7man

Probably because they know more about the weather than egt's....

Old Slow Coach

I can imagine that will give you a lot of peace of mind when you have your finger on both pulses of your motor! I'm going to add this to my list of things to get done over the winter.

Howard Coleman

iTrader: (6)

fyi, i did receive a number of PMs re my Greddy gauges and am shipping them to first come so pls no more emails

howard coleman