I'm sorry this may be a redundant question but why does the pyromiter(splng)prope go pre turbo instead of post turbo? I have 04.5 drw 4by4 with some mods. Hypertech III,ats tranny work, AFE intake, catback banks and some gauges. I pull a fs3000 weekend warrior at about 8000pnds. I can't even run stock with out my egt's hitting 1400 to 1500 going up a silly little hill. Plus it's all the truck can do to maintain 55 to 60 mph. For example, I was heading out of cal on the 10 going up the Indio hill pulling the trailer dry at 6800pnds and couldn't break 60mph.

My brother in law drives and owns his own bigrig and does most of his own mechanical work also. He was wondering why my egt probe was pre turbo on the exaust manifold. He said that all the trucks he has worked on are allways post turbo. I explained to him that we don't want to go over 1300 so it's more important to know the temp going in instead of going out. He then said that even on the big truck it's not advised to go over1300 either. He said that putting it on the pass side exuast bank your only looking at the temp four cylinders instead of all eight.

How are you guys running your programs without the egt problems or do I have the probe in the wrong place. I'm tired of dodges smoking me up these hills pulling roughly the same load.


Is there a fix?



Boyd

pre-turbo so you know what is going in. Post turbo can be at least 200-300 degrees lower. No hard numbers on the drop through the turbo. Each bank goes to the turbo separately, there is no common pipe. Pick one side or the other. Or both sides and two gauges :-). Tunners can increase the EGT's. Maybe you need to run a smaller tune.

Jim

The turbo is an unknown variable. If you put it post turbo you are getting a reading that has already been cooled an unknown amount by the turbo and all the associated plumbing. The turbo and the heads are what you are trying to protect by watching your EGT's so the most logical place to put the probe is pre turbo.

If you put the probe post turbo you will see cooler temperatures but that doesn't change the fact that you are potentially feeding your turbo Exhaust gasses in excess of 1500 degrees. So if you are post turbo you don't know how much you are feeding the turbo which is what you are trying to protect in the first place. The turbo will absorb and dissipate different amounts of heat under different circumstances so you can't calculate the EGT intake to more then a few hundred degrees.

Pre turbo is definitely where you want to be. Ideally you would have a reading from each bank and possible even a post turbo reading. Better yet a reading from each cylinder. Obviously that is not feasible which is why we do 1 bank which gives us a pretty good idea of what is going on.

If 1 cylinder in 1 bank was producing higher EGT's then the rest you most likely won't catch it with a post turbo reading anyways. Especially after it combines with all the other Exhaust gas and goes through the turbo etc.

**Edit Jholly beat me to it and summed it up very well.

Thx for your reply's. When I'm hitting 1400-1500 on my egt's it's has been with out a tune installed. Don't get me wrong i love my truck but this is damn frustrating. I can't even compete with the dodges running hills pulling the same weight.

It makes sense to me to have it pre turbo but why do the big rigs have it post turbo? It seems to me that a turbo or motor on one of those bad boys is a lot more money to replace than ours.plus it's how those guys make there money.


boyd

There's nothing wrong with 1400-1500 degrees for short periods. The lower the better but the LLY's run a bit hot. I've never heard of anyone melting down an LLY turbo yet.

How long is a good estimate to be able to keep the EGT's up around 1400-1500?

Boyd

bssanders,

You would probably benefit to look at the threads that address cold air intake. There has been a lot of discovery lately on how hi IAT's are getting, that's air box intake temps up to 120 degrees over ambient. That plus poor flow characteristics over the intercooler, are not helping combustion temps.

You will find some of these solutions in the Overheat threads, if you dare look. Set aside a weekend though.

RickD lance did some testing of proposed mods, and had significant improvements in EGT.

bsanders, I maintened ~1400 degrees for 2 hours. I had an emergancy at home and I had tow my camper home into a stong head wind the entire way at around 80mph. This doesn't mean that you should do this but it has been done. I would say that maintaining 1400-1500 degrees for 15-30 seconds at time you should be ok. I would not recommend pulling down the highway for extended periods at anywhere near that temperature.

I live in phoenix where the ambient air can get to 115 easy. Then take into acount how hot the pavement gets. I hope there is some good mods coming out soon. Thx for the imputs.

Boyd

That won't really change EGT's too much. It does have some effect but not as much as other factors.