Exhaust manifold temperature.

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jenand40
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Exhaust manifold temperature.

Post by jenand40 »

Just carried out a compression test of my engine and whilst it was hot thought a would have a play with my new infrared temperature gun. Came across a variation in the exhaust manifold flanges which I cannot understand, with engine hot, idling the lowest temperature was 70 deg.C (no.7 cylinder) and the hottest was 130 deg.C (no.3 cylinder) on the near side bank and lowest on the off side bank was 76 deg.C (no.2 cylinder) and the hottest was 168 deg.C (no.6 cylinder). I would have thought they would all be about the same.
Any thoughts?
PS. The manifolds are stainless with heat wrap on.



stevieturbo
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Re: Exhaust manifold temperature.

Post by stevieturbo »

Unless pointing at exactly same material etc....heat guns really can vary. ie if one was pointed at wrap, and another stainless..or different numbers of layers of wrap.

But most cylinders should be fairly close if measured in exactly the same manner and location. Assuming manifold materials and design wont pull more heat out than some other cylinders
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Ian Anderson
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Re: Exhaust manifold temperature.

Post by Ian Anderson »

What inlet and carb are you using.
With some manifolds and 4 barrel carbs, if not set up right some cylinders could run lean and others rich.

Could give readings as you suggest

Ian
Owner of an "On the Road" GT40 Replica by DAX powered by 3.9Hotwre Efi, worked over by DJ Motors. EFi Working but still does some kangaroo at low revs (Damn the speed limits) In to paint shop 18/03/08.

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Re: Exhaust manifold temperature.

Post by SuperV8 »

When I had intermittent running issues with my megasquirt - I would use the exhaust temperature to quickly tell which cylinders where down/not firing correctly.
My wrapped stainless headers - the hot ones where hot enough to lightly 'singe' my fingers, while the cylinders which were not firing correctly could be touched without singeing!

Do you have any miss-fire or rough running?
Dax Rush 4.6 supercharged V8 MSII

jenand40
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Re: Exhaust manifold temperature.

Post by jenand40 »

The temperature was taken at the same position, top of exhaust flange, on each cylinder.
Engine is a Rover 4.2 with Hotwire fuel injection.
Idle is steady at 700 rpm (Tornado chip) and all spark plugs are the correct colour.
Car has not been on the road with this engine fitted so maybe I ought to see what she performs like when I get her insured.
Not really worried, as long as she performs all right on the road, but just thought it a bit odd and would like to have understood why.

DaveEFI
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Re: Exhaust manifold temperature.

Post by DaveEFI »

Hotwire is batch fire with two injector drivers - one driving the left bank, the other the right. From that, the only difference in fuelling could be down to individual injector flow. And if the plugs all look the same colour, unlikely to be a fuelling or ignition problem. if things appear to be normal, they likely are. :D
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stevieturbo
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Re: Exhaust manifold temperature.

Post by stevieturbo »

jenand40 wrote:
Thu Jun 20, 2019 12:17 pm
The temperature was taken at the same position, top of exhaust flange, on each cylinder.
Engine is a Rover 4.2 with Hotwire fuel injection.
Idle is steady at 700 rpm (Tornado chip) and all spark plugs are the correct colour.
Car has not been on the road with this engine fitted so maybe I ought to see what she performs like when I get her insured.
Not really worried, as long as she performs all right on the road, but just thought it a bit odd and would like to have understood why.

If you mean the actual thick flange that bolts to the head....I would not consider that a reliable place to take a reading.

It would need to be on an actual tube, thinwall or similar to get any indication of what that cylinder is doing. The flange is too thick, too close to the head etc with too much ability to have heat drawn away from it because of those reasons.
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bigaldart
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Re: Exhaust manifold temperature.

Post by bigaldart »

If you haven't found a solution then forget idle temperatures, if you even them up you will often find big differences at higher rpm. It is far more important to have equal temperatures at the rpm you run regularly.

Mc Tool
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Re: Exhaust manifold temperature.

Post by Mc Tool »

I been wondering about this batch fire efi . I expected the fuel shots would be timed for each cylinder, before I got the ms and saw only 2 injector feeds. Gotta say I was a bit dissappointed to find my new toy was pretty budget.I thought the whole point of efi was to deliver a computer controlled accurate shot of fuel . Anyhow it would seem that each of the 4 cylinders on either of the 2 feeds from the ecu get their fuel at different points in the cycle. I can see that with a few revs on board things might "even out " fuel wise .....but at idle the misstimed shots ( lets assume that one of the 4 shots might be at optimal timing for that cylinder ) have more time to bugger things up. Im thinkin that if one cyl got its shot at the point where the inlet valve is just beginning to open and another got its shot just after the valve had closed (1/2 a turn later ).....could you reasonably expect these 2 cylinders to behave the same, specially at idle :) . Why not wind her up to 3 grand and retest to see if things even out a bit
I wish I was young again , Id be heaps smarter than the first time

DaveEFI
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Re: Exhaust manifold temperature.

Post by DaveEFI »

With batch fire on MS, you get the choice of alternating or simultaneous and how many squirts per cycle. On my SD1 and MS2, I settled on alternating and two squirts per cycle.

What I did change over the original Lucas injection was the injector grouping. Instead of left and right banks being grouped to a driver, I followed the firing order.

Image

Can't swear it really makes a difference, but I've persuaded myself it gives a better idle and low revs grunt. But costs nothing to do.

MS3X will give you fully sequential timed injection. But you'll also need a cam sensor. Opinion seems mixed about if it is worth the considerable extra cost. On a modern engine, it's more to do with emission control.
Dave
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Mc Tool
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Re: Exhaust manifold temperature.

Post by Mc Tool »

Well thats me learned. Makes more sense ,Thanks Dave ,Im happier now :D
I wish I was young again , Id be heaps smarter than the first time

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