Hot Bank ?

[900ss]

Hi
Can anyone suggest why the o/s exhaust manifold on my 4.0 engine should be running excessively hot? The engine actually appears to be running very well with no obvious faults, but as it is within 10 mins of it running from stone cold (at tick over speed only!) the heat generated from the o/s manifold is unbelievable! Like you cant put your hands within 3" of it! I've used heat insulation wrap on the manifolds to help shield the heat away but the o/s manifold has already turned the once light tan colour lagging to almost toast brown, yet the n/s manifold is much cooler with way less discolourment of the lagging!
This is all at tick over speed under no load which is really puzzling me
Any suggestions?

Ps, All cats have been cut out and it runs a straight through 3" exhaust, so it cant be any of those causing a restriction, but I don't know if they could cause a knock on fault elsewhere?

[Devil's Advocate]

Could it be that the other bank is just not as hot (they normally both get VERY hot! Try using a tie-wrap to check the ex manifolds as you start up - it should melt and "slip" on contact (within 30 seconds or so of starting the engine up) on all cylinders (and you can check them all in the space of 20 seconds so variation across cylinders is negligible). Otherwise, has the engine had any kind of rebuild (one head off, reskimmed, higher compression ratio... bit of a long shot though)?

[900ss]

Cheers
Yes the engine has been rebuilt (previously in its life) but as it runs well I cant see the n/s bank being at fault?
The tie wrap idea is a good one
I will try that next

[IPAddis]

Have you removed the lambda sensors and switched the ECU into non-cat mode? Excessively warm manifolds might be excessive fuelling (I think).

Ian A.

[chassis 33]

Could it be a blocked injector or injectors causing a cylinder or cylinders to run lean and raising EGT in that bank? Is there even a hint of detonation/pinking?

Regards
Iain

[dlewis]

or an inlet air leak?

I assume that, if you are are continuing with the wrapping on the exhaust, there is some symmetry in the amount/ position of the wrapping?

Dave

[900ss]

Ian A
I’m still using the lambda sensors as I assumed it would run better/need to use them? I wasn’t aware I could switch the ECU to a non-cat mode? How?
Btw, I assumed if an engine was over fuelling it could actually run cooler not hotter? (unloaded @ tick over speed) happy to be told otherwise.

Iain
The engines only been revd unloaded atm, so no audible pinking Also all cylinders are firing by what appears to be equal amounts possibly ruling out injectors? I would like to change injector bank for bank just to see, but as the n/s aren’t the easiest to get at I haven’t braved that one yet lol

Dave
No audible or obvious air leaks. The engine revs freely and returns straight to tick over speed without any hunting.
Yes the manifolds have been equally wrapped

[victormeldrew]

I bet its not running as hot as mine - my headers are glowing red. She's not well!

[chassis 33]

Too much retard on the dizzy will cause that, also check for the two machine screws holding the vacuum advance onto the dizzy, this being loose gives what seems to be similar symptoms to a failing pressure regulator (lots of lean running and high EGT), send the timing all over the place. It's what cost Graham Walden the class B title in the TVRCC series this year!

Take a plug/the plugs out. Sooty is rich, off white glazed is lean, slightly mottled brown is about right, sooty around the metal parts and a glazed core is detonation.

Regards
Iain

[GreenV8S]

If you run it open loop you will kill the lambda sensors (if retained) and cats. That's rather an expensive way to diagnose fuelling faults.

[900ss]

I'm glad mine aren't running red, it's already bubbled some paint as it is lol

Thinking about it the vac unit I know is slightly wobbly, but I think only in the rotational plane? Something else to check this weekend then.

[chassis 33]

The vacuum advance is only held in internally by gravity onto the plate, no clips or anything fancy like that, if it an move up and down it may of popped off the plate.

But all this fails to explain why its only occuring on one bank.

Regards
Iain

BTW Peter, any change you could cast an eye over the tread in the engines forum for my, see if your V8 knowledge can help?

[900ss]

GreenV8S said:

If you run it open loop you will kill the lambda sensors (if retained) and cats.

Sorry I don't know the meaning. Please explain open loop.
No cats fitted but retaining the sensors (they help fill the holes lol)

[IPAddis]

900ss said:

GreenV8S said: If you run it open loop you will kill the lambda sensors (if retained) and cats. Sorry I don't know the meaning. Please explain open loop. No cats fitted but retaining the sensors (they help fill the holes lol)

Open loop means that the ECU is not adjusting the fuelling based on inputs from the lambda sensors. I'm not suggesting you do this (although I understand it's beneficial in getting flames from the pipes!). I just thought you might have had non-cat manifolds fitted with no lambda sensors. In this case, if you don't switch to the non-cat mode, the ECU gets mighty confused!

If you have it in cat mode and have retained the lambda sensors, it should be OK.

Ian A.