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Discussion Starter · #1 ·
After doing some monitoring of exhaust temps on each cylinder, I've found them to differ upto 200degsC

An example would be, say,

1=598
2=644
3=630
4=683
5=723
6=774

Running 1bar @ 7000rpm

Thats using a STD plenum with an 80mm single throttle welded onto the front.

Does this seem a little odd??

Any comments??
 

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Seems natural for them to get hotter towards the rear of the engine bay... less cool air getting in.
 

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A good example of the standard plenum causing a leaner 5th & 6th ?????

I look forward to seeing what difference your new plenum will make to the ex temps front to back.
 

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Yea, Gotta agree with leggus here, Wonder if anything like that happens on the inlet too ?
 

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?

leggus said:
Seems natural for them to get hotter towards the rear of the engine bay... less cool air getting in.
Bollocks!

They will get hotter at the rear because of greater airflow, as a consequence of the inlet plenum design.
 

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R32 - thats not right. Maybe the tips are in different positions relative to the gas flow, also as they start to fail the temp readings start to drop from actual.

Std R33 GTR shows aprox 30C difference No1 to No6 (3% different airflow).

Your talking nearly 30% difference in readings. Over 30% difference in AFR across cylinders would be noticable in tone / smoothness of the engine as a whole, that would suggest 11:1 to 14.5:1 spread ie one or more dead cylinders when on boost.

Also for 1 bar boost those temps are very low, what diameter thermocouples are they? Have you used temp compensated cable to connect them all? What readout are you using?

Sure its not he AEM providing different spark timing to each cylinder?!!!!!!???
 

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Discussion Starter · #7 ·
The thermocouples are type K. 3mm dia. Inconel.

Positioned here



Thermok is the display equipment being used.

I have used proper thermocouple cable to extent cable length, although only #1 has been extended.

Is the AEM providing crap spark??? I really don't know, I have no back to back comparisions.

After trimming the fuel and ignition on each cylinder(#1 & 6) the temps are now within 40degsC. An acceptable variation.

It would seem that the temps are most consistant on either full boost or -4 to -10psi MAP. At around the 0 fig is where it seems most uneven.

I've noticed a slight exhaust blow on cylinder 1 which will be affecting the temp giving a bum reading.

The investigation continues..
 

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3m is the `right` size to use and proper cable as well. The position looks consistent - are they supported in the vehicle? They really dont like vibration along the free ends. I guess you can trust the EGT readings.

What AFR are you running (ref the low temp readings)? If its really rich as suggested by the temps, you may be getting some fuel mist coming through which may impact the EGT readings (but it would have to be getting on for 9.5 / 9:1).

You know the `issues` with AEM. I`ve just finished my rebuild after 3months of AEM use.......mapped by the same person (me!)to the same spec as the PFC that was on the car for 18months with no problems.

1 pistons showed signs of almost PI type damage, det cans and knock monitored at all times.......I really do not trust the CAS reading / ignition control on the AEM (amongst other things!)

I would be really careful trimming on the AEM to get consistent EGT readings, it may cover an underlying fault.

One of the tuners on here does not supply AEM any more as they also apparently had 1 (or more) engines go with the blame hovering over the ECU...
 
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My

We are getting technical!!!.How about differences in Plug gaps,spark performance,cylinder efficiency, different dynamic compression between cylinders, injector imbalance etc. Oh what a minefield. Oh and forgot abouy the AEM!!!!. Good luck, keep up the good work!

Tony

Ps you should really be looking at the pressure in the different primaries,WOW, sleepless nights! LOL.
 

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tonysoprano said:
We are getting technical!!!.How about differences in Plug gaps,spark performance,cylinder efficiency, different dynamic compression between cylinders, injector imbalance etc. Oh what a minefield. Oh and forgot abouy the AEM!!!!. Good luck, keep up the good work!

Tony

Ps you should really be looking at the pressure in the different primaries,WOW, sleepless nights! LOL.
Is that what being worried about your position sounds like?
 

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SIHethers said:
Bollocks!

They will get hotter at the rear because of greater airflow, as a consequence of the inlet plenum design.
are you talking about airflow inside the engine? i think leggus was talking about airflow within the engine bay, hence the confusion.
 

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Discussion Starter · #14 ·
I agree, there are loads of factors that can influence exhaust temp.

I think dumping the CAS and running a difference pickup system off the flywheel would be a good idea.(much head scratching)

That would eliminate the AEM CAS issues.
 

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R0B said:
are you talking about airflow inside the engine? i think leggus was talking about airflow within the engine bay, hence the confusion.
Thanks ROB, i was indeed talking about the engine bay, and not the plenum inlet temps.
 

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R32 Combat said:
I agree, there are loads of factors that can influence exhaust temp.

I think dumping the CAS and running a difference pickup system off the flywheel would be a good idea.(much head scratching)

That would eliminate the AEM CAS issues.
eliminate the AEM mate!!!!!!!!!!!

and yes the rear cylinders will run hotter because of the engine bay cooling and engine cooling,,,,,,, i dont think plenum design has jack shit to do with it....but hey feel free for all you to grill me if you wish...... why do the rb20 and rb25 do the same thing??????? start your car up, let it idle for about 30 mins with the bonnet closed, then check your temps,,,,,, bet you they get hotter to the rear,,,,, so there goes plenum design out the window..... since every cylinder will be sucking in it own air supply........
 

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its been so many years since this post but interested how much percent of fuel did you add on each cylinder to make it even if you remember.


The thermocouples are type K. 3mm dia. Inconel.

Positioned here



Thermok is the display equipment being used.

I have used proper thermocouple cable to extent cable length, although only #1 has been extended.

Is the AEM providing crap spark??? I really don't know, I have no back to back comparisions.

After trimming the fuel and ignition on each cylinder(#1 & 6) the temps are now within 40degsC. An acceptable variation.

It would seem that the temps are most consistant on either full boost or -4 to -10psi MAP. At around the 0 fig is where it seems most uneven.

I've noticed a slight exhaust blow on cylinder 1 which will be affecting the temp giving a bum reading.

The investigation continues..
 
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