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EGT temps cruising at 80mph?

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Old 09-16-2002, 09:22 PM
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Default EGT temps cruising at 80mph?

Does 1400 - 1450F sound too high?

How long do you guys usually boost for? On anything higher than 10psi, I can boost for only about 5 seconds before the EGT flies to 1550F, then I shut it down.

Sorry for the EGT's revisited post again.
Old 09-16-2002, 09:46 PM
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Default Re: EGT temps cruising at 80mph? (shamoo)

yeah, that seems too high man. I know mine goes to about 1100F when I'm going uphill for a while (not boosting)...when I go through 1-3 gears I get near 1500 depending on ambient temp. I'd like to hear some other temps to make myself feel better, as well. Mine still seems too high for running insanely rich.
Old 09-17-2002, 06:51 AM
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Default Re: EGT temps cruising at 80mph? (ion_four)

If you know you are running really rich you may what to bump you timing up a bit, your higher egt's could be form the unburnt fuel in your combustion chamber being burnt in your exhaust manifold.
Old 09-18-2002, 06:03 AM
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Default Re: EGT temps cruising at 80mph? (turbosol)

If you know you are running really rich you may what to bump you timing up a bit, your higher egt's could be form the unburnt fuel in your combustion chamber being burnt in your exhaust manifold.
Advance my timing? I always thought it was retard the timing. Under boost, my timing is very advanced according to the OBD tool my friend has on his laptop. However, the A/F ratio is perfect. Then I come across this:

There is a gross amount of misinformation floating around about exhaust gas temperatures. I have posted many times explanations to EGT questions. But it seems the search feature here tends to overlook them for whatever reason. I have found an excellent article done by the fine folks over at Simple Digital Systems. It is written in plain English, and is 100% correct. The link is http://www.sdsefi.com/techegt.htm and for those of you that are lazy to click, read below and learn!
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 the 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 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 11.8 and 13 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.

Are EGT gauges better than AFR meters? Conventional narrow band oxygen sensors and digital LED meters are not the best devices to measure AFR in the richer ranges but they certainly warn of a too lean condition immediately and obviously, without translation by the driver and they are affordable. Meters combined with wide band sensors are laboratory quality usually, highly accurate and useful but very expensive and sometimes bulky. EGT gauges have the limitations above and are generally priced between the other two. I would suggest that the two types are complimentary. EGT gauges have the advantage of working long term with leaded fuel which will clog oxygen sensors. EGT gauges are widely used to set mixture on engines used for steady state high power applications where operation has been carefully documented such as in aircraft. The choice would depend on the application. Both are better if you can afford them.
What do I do?? Is dyno the only answer?
Old 09-18-2002, 08:58 AM
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Default Re: EGT temps cruising at 80mph? (shamoo)

When cruising at 80mph, they stay at around 1400-1500 depending on how much load is put on it, but when accelerating in 5th gear, they never go past 1500 before I have to shut it down around 130mph or so
Old 09-18-2002, 09:20 AM
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Default Re: EGT temps cruising at 80mph? (B20LS-T)

my EGT cruising at 80 in 5th is at 1350-1375. On boost (10psi dragIII B18B) it first drops rapidly to about 1200 then increases to 1375. It does not go beyond 1390 with these injectors (continuous 10 psi boosting). However, if i only boost to 7 psi my egt drops to about 1200 then increases to 1250-1290. Previously, with 6:1 and 310 cc i have seen in rise to 1450-1475. Now, I am using 8:1 with RC 310 cc. Base fuel pressure is set to 33 psi., timing is at 14 BTDC, and my EGT probe is located 1.5-2 inches away from #4 exhaust port.
Old 09-20-2002, 08:11 AM
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Default Re: EGT temps cruising at 80mph? (modvp)

What promted you to put your probe in #4? I have mainly seen #3 and sometimes #1.
Old 09-30-2002, 06:07 AM
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Default Re: EGT temps cruising at 80mph? (turbosol)

On my previous manifold (cracked), I had the probe in #3. On the new manifold, I placed the EGT probe in 4 because I wanted to compare EGT temp. I saw no differences in EGT temp. between 3 and 4. Therefore i left it in 4.
Old 09-30-2002, 06:38 AM
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Default Re: EGT temps cruising at 80mph? (modvp)

here is what i reported on my thread about stock EGTs

https://honda-tech.com/zerothread?id=288343


"80mph highway cruise: ~700C"

which converts to about 1300F

just fyi.
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