questions on integrated wastegates and EGTs

[formula]

Ok, here it goes... ... ... .

On a *divided* turbine housing with an integrated wastegate, only the aft 3 cylinders are wastegated. This obviously will slow the turbo down enough to keep it from going into orbit, but what about EGTs? If you're at WOT and the wastegate is opened, then wouldn't the forward 3 cylinders be getting some pretty toasty EGTs? Assuming, of course, that the pyro is in the aft half of the exhaust manifold. Maybe I should stick the pyro in the front part of the manifold. What would be the consequences of using a non-divided wastegated housing? Should I even be concerned with this at all?



Cheers,

Sean

 

[LSMITH]

Since the front three cylinders are providing all the drive pressure (or the vast majority of it) they are getting all the back pressure too when the wastegate is open. I too think the EGT is higher on the front 3 in this case, but don't know what effect it will have. Stick another probe in the front runner and hook it up to a pyro right next to the one you have. Go out and flog that thing for all it is worth and get back to us with some data



Just kidding but I wonder about it too. My gauge needs an amp on the TC so adding another probe would be rather expensive. It never crossed my mind when installing the probe that the wastegate was on the rear 3 cylinders and all of the instructions I have ever found say to put it in the rear runner anyway.



I have taken the position that unless you are running against the wastegate AND holding EGT of 1350+ for at least several minutes there is no harm possible. The only way to find out though would be parallel pyros I think.

 

[drees1]

I'm betting that there is very little difference front to rear on the temps. Remember, the heat is generated by combustion in the cylinder and both ends get the same air. Only a free er flowing rear cylinder would benfit during the valve overlap period only with slightly improved scavenging. Since a small amount of waste gating results in a big drop in boost, there is still plenty of exhaust going to the turbine on both sides. I have seen posted the #1 cylinder is hotter due to flow problems, too. Surely someone here has measured both. Lets hear the results!



Doug Rees

 

[formula]

TTT

 

[nickleinonen]

how about going into the manifold and turbine housing with a grinder and removing some of the web between the front 3/rear 3 cylinders to more or less make it equal pressure to turbine. .

 

[HVAC]

Twins

This becomes even more important when building twins. We are concerned about drive pressure and avoiding the blown headgasket dilema.



Two years ago I ruined a few housings this way