EGT sensors on 1st Gen ITA?

[ishod]

Do you feel they are a necessary item to keep the carb tuned properly? If yes should two be used, one for each header pipe? Suggestions for brand/model?

they are essential to getting your car up to speed, and yes you need 2, I didnt have them so I paid to have my car chassis dynoed, but any change in elevation or temperature and your money is wasted. Buy the digital dual readout EGT and get a box full of jets and keep going smaller till your EGT'S read 1450 at the end of the straight, check your timing often, 25-26 tops, no more, detonation will destroy your motor. Im not an expert , yet, others can bring you in closer, dont let my trends post discourage you, remember were racing for a three dollar trophy to have fun.

I cant believe 2 weeks past and nobody came to your aid on this, were slackin guys

[Festus E. Simkins]

There is probably some disagreement regarding the optimum exhaust temp for a rotary engine. I believe it is close to 1550 to 1600 degrees F can't really remember. You might want to check with the guys at mazspeed.com. Also, Westach makes a duel guage that goes to 2000 degrees F. That is the one I use. I have seen exaust temps as high as 1900 degrees and the engine lived. I rejeted to get them down. I am still running a little high be I haven't had any problems so far. Just my .02. There are guys out there FAR smarter than me on this subject.

Drive well.

[tdw6974]

Lets see if this works http://www.aircraftspruce.com/home.php this is where we got our EGT with probes as I recall some are packaged with probes and thats what you will need. T weaver

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Tom Weaver: Logistics & Technical Support Manager IE truck driver for 1980 RX-7 ITA #63
"Hemi haulin' Rotary"

[L.Lamb]

So where do you get this box full of jets????

[ishod]

Thanks for the input everyone. Whoever rebuilds your type of carb should be able to furnish various backup jets.

[Marcus Miller]

<-- knows nothing about EGT's

How far from the ports should the measurements be taken?

Marcus

[This message has been edited by Marcus Miller (edited February 28, 2004).]

[lateapex911]

The problem is that I rebuild my carb, and I don't know where to get a box of jets, and Mr Yaw rarely returns my email.

I'll measure this weekend, but my WAG is 18"-24" down the header. Stay tuned. I got mine from Aircraft Spruce as well.



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Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]

[ddewhurst]

Jake, try Dave Lemon at mazdatrix.com ??????

[Marcus Miller]

Hey Jake,

Did you geta chance to measure the distance on those EGT sensors?

As for jets, I get mine from Yaw, he has always returned my calls and emails(?)
thanks!
Marcus

[Jim Susko]

They are essential if you want to make power in various climactic conditions.

The temperature can be different for different cars depending on where you mount them and other factors. Festus (Hi, Festus!) is probably closer on temperature. The secret is to dyno them and note what they are when you make the best power. Then, when the temperature, humidity or barometric pressure changes, change your jets to produce that temperature, and you are back in the power.

Simple!

Jim Susko

[Tak]

Webber DGV jets fit the mazda carbs.
Contact Overseas Distributing at 800-665-5031.

Tak
#29 ITA SFR SCCA

I said 1450 degrees because you WILL lose your engine (front rotor bearing first) if the rotors overheat(1800), better safe than broke, yes you can get 1 1/2 hp out of that last 200 degrees but at a price. If you could garrantee the temp would NEVER exceed 1650 I would say set it to 1600, but in the real world........

Dave Lemon is the best person to answer this question and in time I believe he will chime in here to give us his very experienced opinion.

[Jim Susko]

[quote]Originally posted by 7'sRracing:
"[B]I said 1450 degrees because you WILL lose your engine (front rotor bearing first) if the rotors overheat(1800), better safe than broke, yes you can get 1 1/2 hp out of that last 200 degrees but at a price. If you could garrantee the temp would NEVER exceed 1650 I would say set it to 1600, but in the real world........"

Hey, 7's: Before I dynoed I used to run up to 1950 degrees. Never a problem with the motor. Now after dynoing I run 1650. So I say again, it depends....

You MUST dyno to really know. If you use an arbitrary number from someone else's engine you are deluding yourself and may burn one up at a 1200 degree reading if the sensors are placed differently. There are no shortcuts, and copying does not produce results. Only TESTING produces numbers that are meaningful.

Jim

[moto62]

Originally posted by lateapex911:
The problem is that I rebuild my carb, and I don't know where to get a box of jets...

Try Fast Freddie's in Calif. 714-540-3801. A little late on the post but still may be helpful.
Ray

thanks Jim, like I said earlier, I didnt have EGT's in the car and relied on the sensor's from the chassis dyno we were using. Im not even sure the temps stayed the same from dyno time to race time but rest assured I wont make that mistake again. all I can say for sure is I have 2 completly junk engines from overheating the rotors, whatever the temp was.

help me determine what killed these engines if it wasnt excessive combustion temps burning away oil from the rotor bearing.

engine water temp never went over 195 and was full

oil pressure was 80 psi at idle, 120 psi at at 5000, 80 psi at 8000. im told this was due to areation (yes the engine did have de-areation plate)

oil temp was 200-210, engine never taken above 5000 rpm until the oil temp reached 180 deg

engines had the trick maz comp race bearings, e-shaft jets and were balanced

both engines had a cup of metal sitting on the de-areation plate under the front rotor.

[bcarter]

I haven't used them, but they sound like a good idea.

Where do they go? Do you drill into the headers, and how far from the block to you do it?

Thanks

[Jim Susko]

If you had oil and water temps that were ok, and you dynoed the motor for best power, that suggests to me it was not mixture that killed the motor. Exhaust temperatures would not change THAT much and high combustion temps would generally result in apex seal failure, not a main bearing failure.

Your oil pressures sound like you may have the special higher pressure oil regulator. Be careful with this. If you are using the stock under-the-ratiator oil cooler, those higher pressures will lift the thermostatic oil bypass spring off it's seat and route all of the oil past the radiator. You must remove the bypass and put in a solid needle valve to make sure the oil will not bypass. However this still does not sound like your problem. If it were, more likely you would have lost an apex seal first, because oil is their only source of cooling.

Another thing to check, but again a long shot, is water cavitation or aeration because of high rpms. Aerated water will not cool even if the temperature is reasonable. I seriously underdrive my water pump and alternator by using the small competition aluminum crank pulley from MazdaSpeed and by fitting a stock crank pulley on both the water pump and the alternator. It takes a bit of fabrication using a lathe to cut the centers out and careful welding to the stock water pump hub but it works. Takes less HP to drive, too.

Mazda says "if you are using a stock cast iron [water] pump, we recommend gutting the stock thermostat, leaving just the thermostat casing. Because some restriction is helpful, generally removing the thermostat is not as effective as using a gutted thermostat..It is also important to plug the thermostat housing's water bypass. This can be done..by tapping the hole (1/2 inch pipe tap) and installing a plug."

Again, however, since oil temps were reasonable this does not sound like the problem either.

Perhaps the bearings just failed because of improper installation or debris left in the oil passages from a previous failure and rebuild. It may be as simple as that. Once a bearing starts galling from any source, it is just a matter of time before it fails.

Jim

[dyoungre]

I too had the exact same failure in september- after never failing an engine in 4 years, I failed 2 in 2 weekends. Front bearing spun, copper plugging the oiling holes on the crank. No symptom until 1/2 lap before seize. If ANYONE has an idea of what happened, I'd really like to know. I'm adding an oil pressure light to go with my gauge, as I don't tend to check 'mid corner'...

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Dave Youngren
NER ITA RX7 #61