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B Series ITB Tuning issues

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Hi All,

Have recently just done first start on my na Individual TB'd B16B which is fully built motor which is cammed.

Tune is VE Model with Aphla N TPS as load axis. Vacuum is stored in a vacuum container and this goes to each runner. The FPR does not connect into the vaccum container (because my the people who made my ITBS advised against this for NA builds is this correct?)

it started up okay a bit lumpy I believe this is to expected with CAMs like this. Once I increased the revs to about 1200 it seemed pretty smooth and okay.

MAP at idle is -1.5 psi avg, Fuel P was 40 psi avg. Oil pressure seemed high at 85 plus psi my engine builder said this was due to the oil being cold and should reduce once up to temp. Coolant temp started to get up about 40 and was slowly rising as expected.

The problem I was noticing first was that I couldn't seem to get a lambda value of 1. After a few trys of increasing the VE table to at 70 I got 1.1.

The second problem was that cylinder one and two exhaust manifold where getting hot but cylinder 3 and 4 where still cool.

The first assumption with that is that the itbs are incorrectly calibrated but im not sure. I have tested all the spark plugs and on the ecu all injectors seem to have duty cycle when the engine is running. No trigger errors.

I really didnt want to keep running the engine which the two getting much hotter than the others so I have turned it off and come to here for advice.

Any help would be much appreciated .


If your injectors spray below the throttle, then you want to reference your fuel pressure regulator to manifold pressure. This will just cause errors in trims if you don't and you will just end up "baking in" those errors. Personally, I prefer to get a 10% fuel increase if that's requested at all manifold pressures.

If the injector spray to atmosphere, (ie, above the throttle), then it is OK to reference the fuel pressure regulator to atmosphere.

Are you sure the MAP sensor is configured correctly? Does it read 0 psig with the engine stopped? Is there a reason you aren't configuring the MAP sensor as absolute pressure in kPa? I would expect near 100 kPa stopped (depends on elevation and baro pressure that day), and 40-60 kPa while idling (-8.8 to -5.8 psig). If it is really reading -1.5psi you may have a manifold leak, or the throttle is very open.

Regarding the uneven temps. You may not have your ignition or injection configured correctly. Firing order, batch configuration vs. sequential, etc. Use whatever diagnostics you have in the ECU to verify the correct cylinders are getting fuel and spark.

Have you checked the base ignition timing?

With ITBs, my first suspicion is they aren't syncronised properly - the manufacturer should have a guide and it normally requires a tool to measure airflow, I use one of these - https://www.cbperformance.com/product-p/6537.htm

If you don't have that, or just want to get the engine running, there should be a series of adjustments between the bodies - back them off and set the one the throttle linkage is attached to to a set clearance between the butterfly and the body of, say, 20 thou', using the idle screw. Then set the one next to it to the same clearance using the adjustment between the first and the second, then the next and then the last. recheck to see they're still all around the same clearance and try starting the engine. You may need to adjust the idle screw, but that should at least get it running, but if that fails, then -

As David said, go through the injection and ignition allocations and make sure the correct thing is driven at the right time. Until you get all four firing correctly you WILL find you have a very lean lambda, because there's unused oxygen in the exhaust gases.

Spark plugs give a lot of information - what do they look like? 1 & 2 dry and coloured, 3 & 4 wet with fuel?

I'd start with a simple swap of the #3&4 coil wiring, if it runs on all 4, problem solved. If not swap them back and switch the #3&4 injector wiring and try that, if no change leave them as that and swap the coil wiring again. NOTE, you should be able to do that in the software, which should simplify things.

If you were SURE you had the wiring correct, it could be faulty injectors, but that'd be very unusual to have 50% failure rate - check by swapping 1&2 with 3&4.

Thanks for the replies. I will firstly calibrate the ITBS as they did supply a syncrometer.

@David In the haltech software should the pressure units can be changed to look at absolute values, but then all the sensors will be in absolute. Is the correct way to this. The sensor is from AEM and I calibrated it via there sheet which started off at -14.7.

@Gord All the spark plugs had the similar amount of fuel, but 1 and 2 much more brown colour as 3 and 4 almost no change in colour.

Will try some of these suggestions tonight and let you know how I get on.

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