6 replies to this topic

[Birdie75]

Original Tune:

EJ205 WRX , stock internals, manual boost controller, VF24 turbo, aftermarket exhaust manifold, up pipe, bell mouth down pipe with a Fujitsubo cat back exhaust. Achieved 298hp @ wheels on 17psi.

Not long after that the turbo died so i replaced it with a VF23 (VF24 no longer available) and I removed the cat and restrictor pipe and replaced them with a 100cpsi cat only.

Time passed and I had a little front end accident (didn't stop in time when a rear ender happened in front of me).

On collecting the car she backfired 30secs up the road quite loudly and again 5mins later, still backfires often but not as bad, vacuum is now at 20psi but used to sit st 15, feels a bit sluggish but i haven't been thrashing it since replacing the turbo as it wasn't re-tuned and I wanted to upgrade the injectors and fuel pump first and had the intercooler pipes modified and shortened in the mean time.

Current Tune with VF23 turbo, Sti injectors, and Walbro 342 fuel pump and an EBC.
270hp @ wheels on 18psi ???

I've dropped 30hp and my tuner is absolutely stumped as to why, no fault codes were found, he strongly believed the timing was out (as did an engine rebuilder when he heard the car idling at his workshop, said it sounded too smooth for a Subi) and maybe jumped a tooth or the timing belt was put back on incorrectly by the mechanics when the rear timing cover was replaced.

He's checked everything from cam marks (twice) and crank marks and even counted every tooth on the belt, got the cam specs to check the TDC, pressure loss from the FMIC, pressure tested all pistons with an average of 160psi, inspected the cat and done a run straight out of the dump pipe just in case  (lost power), called a few tuner mates as well and anything they've suggested he's already checked.
The car runs fine, no spluttering, no hesitation, starts easy just less power than before.

He's been tuning cars for 15 years and seems quite knowledgeable and passionate about his work but this job has him scratching his head.

I'm nearly 2 grand out of pocket for all the checking and Dyno runs he's had to do and I'm still down on horses with no explanation as to why !!.

[Barbbachello]

Same dyno, weather, humidity and 900 other conditions? Otherwise its near impossible to compare dyno runs. 

Also welcome

[Birdie75]

Same town, same Dyno, same time of year, 1°c difference from last tune.
I could understand 5hp difference if the weather was different but 30hp with bigger air and bigger fuel ?
Thanks for the welcome too

[Jimbo]

Has the ECU actually been tuned for the mods or have you just put the mods on and hoped the ECU will figure it out?


Also remember it's not the same turbo or injectors against the last run. With changes like that you're unlikely to net the same result. You may have lost some hp but you might have gained some torque. 

It's pretty open ended....

[Birdie75]

ECU has been tuned for the mods, the tuner fitted the injectors on the day of the tune, he said i can fit the fuel pump no worries but do not try to fit the injectors myself and attempt to drive it.
The last engine died from piston failure due to detonation thanks to the previous owner not having it tuned properly.
I've consulted my tuner before I do anything as I'm not pretending to know what I'm doing and risk blowing another engine

[duncanm]

tyres pumped up the same?

cam or crank sensors get damaged in the frontal ?

alternator still ok and pumping out 14.7V (or whatever it should)?

Spark strong?  

Same fuel quality?

What do the two dyno charts look like?  Peak number isn't that meaningful.

How do the two tunes differ? Should only be significantly different in fuelling to accommodate new injectors, right ?

 

Your repairer hasn't done a dodgy on you in some form or other have they (far fetched, but I've heard some horror stories).  Check your block number and 

[Birdie75]

Hey Duncan, the Dyno he has is the one that bolts to each wheel individually.
I was thinking spark a faulty sensor myself as the air inlet on this turbo is exactly the same as the one I replaced so there should be no change to air.
The fuelling should have improved as there is less stress on them and they aren't running at max anymore.
I only use 98 in the Rex and both tunes were done on this.
The tuner said it wouldn't be a sensor or it would have shown up but I've seen different this kind of thing before on other forums where there was less spark on one coil but not low enough to throw a code.
I did have a crank angle sensor code come up not long after the accident but once it was cleared it hasn't come back, i told the tuner this and he said it would have thrown a code if it was rooted.
I will look into the spark a bit more i think...thanks