EGT, worth it or no?

[Nate1647545505]

Hi all,

 

I got tired of using piggy backs and purchased some software to recal the VCM of my ghetto hooptie. I have wideband 99.9% on the car as of now, and was told to look into an EgT gauge for extra safety.

 

I know that putting probes in all of the 6 header primary locations would be ideal, but would running a single probe on the leanest cylidner even be worth it?

 

Edit: Also what temps should I look for under WOT?

 

Thanks!

-Ramathorne

[BiG BeN]

you won't need it with the wideband,and the EGT is hard to tune with anyway.there's too many variables. is it hot because your timing is advanced?retarded? lean?...i don't like them. and noone can tell you what it should read from the get go,because odds are noones probe is in the exact same spot. 2 inches on the manifold makes a significant change to the temp read on an EGT.

[Nate1647545505]

Originally posted by BiG BeN:

you won't need it with the wideband,and the EGT is hard to tune with anyway.there's too many variables. is it hot because your timing is advanced?retarded? lean?...i don't like them. and noone can tell you what it should read from the get go,because odds are noones probe is in the exact same spot. 2 inches on the manifold makes a significant change to the temp read on an EGT.

Yeah makes sense. I was having a hard time deciding if the placement would be accurate, I just want to look for detonation, since it causes EGTs to drop. Also I wanted to make sure I wasn't going to melt anything, I'm guessing there is a temperature at which a cast piston can get dangerous?

 

as far as how they work, taken from SDS EMS:

Tuning Via EGT vs, Wide Band/ Narrow Band Meters

There seems to be a lot of mystery and misinformation about using exhaust gas temperatures to tune engines. Claims by many EGT gauge manufacturers about it being the best way to tune an engine must be qualified. The BEST way to tune an engine is on an engine dyno- PERIOD. What EGT is good for is a reference for where the engine made maximum torque at wide open throttle. Once removed from the dyno, a similar air/fuel ratio can be established at a later date by dialing in the mixture to achieve the target EGT. It is really the AFR that is important, not the EGT. Most engines will make maximum power at an AFR of between 12.0 and 13.5 to 1 however, the EGT may vary from 1250F to 1800F and is dependent on many factors.

 

It should be mentioned that the target EGT is valid only on the same engine configuration as was used on the dyno. If you change the ignition timing, cams, pistons, headers etc., the optimum EGT may also change. Raising the compression ratio with no other changes will drop the EGT at the same AFR. Retarding the ignition timing will generally raise the EGT at the same AFR. One engine might make best power at 1350 degrees while a very similar engine might be happier at 1500. You can't guess at this or you are simply wasting your money on the instrumentation. Wankel engines have higher EGTs than comparable piston engines due to their lower thermal efficiencies. 1800F is not uncommon here.

 

Some gauge manufacturers say you should tune to achieve maximum or peak EGT for maximum performance. This is incorrect. Peak EGT generally occurs at an AFR of around 14.7- 15.0 to 1 on gasoline. This is far too lean for maximum power and is dangerous under continuous WOT conditions. Many people think that the leaner you go, the higher the EGT gets. This is also incorrect. Peak EGT occurs at stoichiometry- about 15 to 1 for our purposes. If you go richer than 15 to 1, EGT will drop and if you go leaner than 15 to 1 EGT will ALSO drop. It is VERY important to know which side of peak EGT you are on before making adjustments. It is safe to say that peak power will occur at an EGT somewhat colder than peak EGT.

 

You can sometimes feel a lean of peak condition as the mixture is hard to ignite and power will be down a bit as well. Once the AFR gets close to 17 to 1 at WOT, generally the engine will start to lean misfire. Most tuners always recommend to begin jetting or programming from a known very rich initial setting and carefully leaning until torque falls off slightly, then going back richer to the point of max torque. Note the EGT at this setting. Be aware that altitude, barometric pressure and ambient air temperature may affect this optimal temperature to some degree.

[el aguila]

I had an EGT and hated it. Was always inconsistent. Do you have any way to monitor your knock sensor (if equipped)?

[Guest Ponyfreak]

EGT's are a better way to monitor yoru engine than a/f ratio. Severe detonation can still occur with the correct a/f

[Mallard]

Everything I know about EGT is what I've been told by a friend with a DSM that does ECU tuning at BOSCH. Obviously you don't want to tune from just an EGT gauge since so many factors could influence it, not just a lean condition. Ideally you would want to monitor each cylinder, but that could be expensive, so tap into the manifold 2-3" from the block on your hottest cylinder. On an I-4 this will tend to be one of the middle 2, on a V6 it would be the middle one on either side, since they retain the heat of the surrounding cylinders.

 

Your AFR's could look perfect, but if your ECU starts pulling timing your EGT's could go up and cause some damage. On the other hand you're EGT's could look perfect and your AFR could be screwed up.

 

Make your own decesion. If you have a scantool that can tell you instantly if timing is being pulled then you may be fine without it. It's up to you, but I will be monitoring both on my car.

[Guest Ponyfreak]

Both is the best of course. Monitoring a/f is cheap. Most engines have a cyl that notoriously run warmer than the others. i.e. #7&8 on the ford modulars. If youare only running one EGT choose that cyl. Best way is to monitor all of them. This becomes costly.

[Nate1647545505]

Originally posted by el aguila:

I had an EGT and hated it. Was always inconsistent. Do you have any way to monitor your knock sensor (if equipped)?

Got one on each bank ( V6 ) , we (in the GP community) monitor Knock Retard like a hawk.

 

I was just looking at EGT to help with timing. I wont have access to a dyno for a bit and would like to get the car dialed in safely.

 

I have a scan tool, as well as the ability to re-write everything in the PCM, from VE to Torque Management.

 

Mallard do you have AIM?

 

Thanks all smile.gif