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Throttle enrichment, Serious issues! Really need help, poss ecu fault? cannot find a solution!


Ryan Simmons
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Ok, i had my 3sgte mr2 in for tuning today with Ryan.G from 2bar tuning. We ran into some issues to which we cannot find a solution!

Quick spec list of the engine..

Gen3 3sgte engine, 2.139 stroker, 1200cc top feed bosh low imp inj's, Simple external fuel system w/bosch 044 and deadhead rail. HTA3582r turbo, Tial 44mm MV-R, 1zz COPs using stock Dizzy sensor as signal pickup. Almost stock head with mild polishing work and upgraded valve springs. LinkPlus G3 ecu.

The Problem...

Basically, giving the throttle a WOT blip from idle obviously should cause an almost instant increase in engine revs. However mine is not quite doing this. Upon flooring the throttle the ECU does not seem to enrich the mixture quick enough to prevent it going lean and therefore causes the revs to bog down a few rpms before picking back up again. Going on and off the throttle at any revs seems to give the same issue and if you was to 'pump' the throttle pedal a couple of times the issue would amplify due to it not having recovered from the first 'pump'. This was never an issue the last time it was mapped and i am using the same fuel system, MAP sensor, TB and TPS. Apart from now having a larger turbo and different bolt on parts, the only thing different from my last mapping session is the addition of some 1zz cops!
My tuner played with all the settings he could think of, we played with fuel pressure, TPS sensitivity, throttle enrichment etc but no joy. We also tested the impedance of the injectors to check they are low and indeed they are.

Not sure if this is related but I did make a slight mistake with the wiring of the 1zz cops, i wired them in back to front (#4 in #1 and #3 in #2) and the same with the injectors, fixing this minor issue did not resolve the enrichment issue and the car ran exactly the same as before; However after doing this, for some reason the base ignition timing then became out by 360 deg and we had to set the cam trigger offset to -360' to get the crank timing mark flashing back at 10' on the cam cover.

Myself and my tuner cannot think why this is happening as everything is working correctly sensor and mechanical wise, It almost seems like the ecu is just responding too slowly to the throttle position change and not adding the fuel soon enough to compensate!

 

Your help would be greatly appreciated!  This project is near complete now and this is the only issue in the way of going for our 500whp goal!

 

thanks

Ryan

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Ok, i shall post to the email address in about half an hour. I will also include a log of what happens when i blip the throttle too, i dont know if the information you need is on there but ill include it anyway. Would it be an idea to record the screen output to show you what the cursor is doing on the fuel table whilst blipping the throttle?

Thanks

Ryan

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could be a couple of things

first the 1200cc injectors what ballasts are fitted and did you use these injectors last time  if the incorrect ballast is fitted then they could be lazy in response especially if the fuel press is up a bit

 or you could have a delayed map reading or possibly a faulty map sensor

i would check that the map signal is not been delayed by some restriction i have quite often come across people using tee pieces that have brass restricors in the centre tail piece this is fine for boost gauges as it smooths the signal but useless for a map sensor

 

hope this helps

regards

David Heerdegen

dave@dtechmotosport.com

www.dtechmotorsport.com

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Hi David,

The 1200cc injectors are top feeds by bosch, low impedance and i have kept the stock resistor packs in place. The car was tuned on these injectors last year and ran fine! They was a little meaty for the job as they only reached a maximum of 63% duty with the old turbo at its maximum efficiency however I chose that size for future upgrading. We double checked the resistance with a multimeter and yes they are Low-impedance. Base FP was set to 30psi.

Map sensor is the 7bar (iirc?) Gold Link unit, which has always been positioned higher than the plenum with the vacuum exiting from the bottom so as not to trap any dirt or moisture in the sensor. ill double check tho that there is nothing blocking it. I have a hunch that one of the T-pieces may be a restrictive type, ill double check.

When i upgraded to Coil-on-plugs i accidentally  wired them up in the wrong order, 1 in 4 and 3 in 2, so the engine was firing from the wrong end first however, strangely enough it ran! The strobe light showed the crank timing mark was correct and the trigger offset was 0 ! This is why i did not realise i had wired them up in the wrong order. My tuner realised this tho at the dyno and we re-pinned the COPs to the correct order;  Afther doing this tho, what  really baffled us is the Ignition trigger sensor then required 360 deg of offset added to it to get the timing strobe flashing back at the correct crank timing point?! We coupled the strobe sensor correctly  -to the coil of CYL 1 (cam end) and with Zero trigger offset set like before when the COPs were the wrong way around, the timing mark was 180deg out on the crank.

I am thinking that i may have also installed the cam belt with the crank 360' out putting no1 on its exhaust stroke whilst the cams are at 0' , with 0 offset also, this would cause the plug to fire on the exhaust stroke in every cyl and the engine would not run, but where i had also wired the Coil-on-plugs in the reverse order, it corrected the phase issue as the engine was firing from no 4 first which should be on its compression stroke (if no1 is on its exhaust).. So the engine would be running from the wrong end first??  So when we corrected the COP wiring, due to the crank being 360 out, this returned no1 to spark on the exhaust stroke of cyl #1 and by adding the 360' offset delay, this put the spark to the correct stroke.  I shall check my TDC of piston 1 at Zero degrees and check if its on the exhaust stroke or compression. If it is the compression stroke then i just have to rotate the crank 360' and re-fit the cam belt, then in theory, Re-set the trigger offset from 360' back to 0'   ....?

 

Does this sound right? and if it is the case, could it cause the throttle up lean issue?  Sorry if that paragraph is quite confusing, My projects dont allow 'Simple' lol.

 

Ryan

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siimon has sent me your log file

quickly looking at it the ecu is doing as asked  although there is a delay between the tps moving and map responding this could be mechanical,  e.g. vac leak to map sensor or restriction.

fuel press seams a little low if that is with the vacc hose off the reg.

has any mapping been done?   how does the car drive and accelerate?

TDC is the same on cylinder 1 and 4   crank doesnt know or care  only the cams dictate intake and exhaust timing

so yes if wired wrong but timing calibration adjusted to suit then yes it would be 360 out.

did you do a test on function to verify that cyl 1 was firing cyl 1 coil  

also firing order set to 1342?

 

maybe post up the map would make it easier.

Regards

Dave

dave@dtechmotorsport.com

www.dtechmotorsport.com

 

 

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Hi Dave.  Good news!  Turns out the problem was in fact a 0.5mm restrictor in the T-piece! i cannot believe that something so simple caused so many issues! I replaced it with a normal 4mm ID Tee and now it revs perfectly. It is over-fuelling by loads now tho particularly on cold start but im guessing that this might be due to my tuner adding loads of throttle enrichment in attempt to correct the problem? Im not clued up in tuning so this is just an assumption. He did tell me when i left that i have to nurse the car home as the mapping is completely wrong, purely for the fact after coming off the rollers we re-pinned the injectors and COPs.

Hopefully a simple tune up on the rollers now is all thats needed to get the car running as it should be!

The only thing i still have not got my head around is why the dizzy trigger needs 358 degrees of offset added to get the crank timing mark in the correct place? I wonder if the dizzy to cam linkage is upside down ? however im pretty sure the connector is offset to avoid this?  The only other way to get the trigger offset back zero is to wire the COPs in back to front again!?

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