202 turbo

[vn5000]

If i run the timing any higher than 10 deg at 200kpa at 4000 it stats to ping ,and im running about 24deg at 100kpa 4000 rpm so i cant add any more timing.It goes well up to 10psi and also up to 14 psi but if you hold the revs for to long at high boost>12-13 it starts to die out .If you back off for a few second and give it to it again it does the same goes good for 3-5 sec then starts to loose power.Also starts backfiring at boost over 15psi and 4800,again initially goes good then starts to die.No probs under 10 psi.Fuel a/f 12:1 when it dies.Cant see anything in logs abnormal.
Iwas thinking maybe weak valve springs alowing the lifters to pump up under boost .Anyone had similar probs
Either that or there is an exhaust ristriction like delcowizzard said.

[Jayme]

ah when he said 10 deg wasnt sure if that was flat 10 deg boost table yeah sounds to me like combo of no intercooler and small turbo, its not going to like to boost over 10psi without a bigger turbo.

[seal12]

just a bit more of an update, i had the exhaust cut off at the muffler which is up front around the gearbox area so it got rid of a fair few bends etc and it acted like a new car again and now will lose traction in second at around 8psi as i have wound the boost right down again.

so for a start i obviously need to get a 3inch system right through and i think this will solve most probs,
and i think i was kidding myself when i asked vn5000 to aim for around 14psi with this setup and am only lucky i havent blown something up in the process
oh'well live and learn.

and all symptoms also point to what vn5000 said about the lifters pumping up coz the springs are to weak,
can anyone recommend what i should replace the springs and lifters with? eg: solid lifters or what rate springs etc? thanks for the help.

cheyne

[Jayme]

yeah small exhaust has similar effect to small turbo, gas cant get out so makes cylinders hot and reduce airflow etc. what size is the exhaust now? if the lifters are pumping up it is rpm based and will happen regardless of engine load. does it lose power when you hold the revs up at light load then stab it ?

[seal12]

my exhaust consists of the usual 6 bolt rear turbo housing witch is a 2.5 outlet i think then goes into a 3inch dump down to the 2.5 straight through muffler and it then went to twin 2in pipes which dumped infront of the rear tyres.

today i removed the twin pipes from the muffler and in place installed a 50cm piece of 2.5inch which basically dumps well before the diff and it lived the engine up heaps,
do you think the rear turbo outlet is another real restriction? but to get rid of that i would have to go to a external gate right coz the actuator opens of it?

if i stab it with the revs up under no load like you said it will go really well for about 3 seconds until it reaches that boost level or restriction but like i said earlyier now one restriction is gone it has already helped alot.

[seal12]

today my turbo spiked at 15psi and a huge backfire came out the turbo and now when ever it spools there is a strange wooshing or whirring noise, any thoughts as to what i have done?

[kojab]

You may have bent the turbo shaft and the compressor wheel could be touching the housing.

[delcowizzid]

ide say its killed the poor t3t4 probably no fins left on the compressor wheel or you could of popped a leak somewhere thats whistleing would be a lean backfire ide say you dont like that engine at all do you its gonna pop soon if you keep driving it hard with no cooler your probably loosing all your power as soon as the turbo heats the intake charge enough it makes the timing way to far advanced killing your power hold it to long on boost and say hello to half a piston melted away LOL

[seal12]

yeah it seems to be getting a bit of a hiding trying to get it right but i guess i am learning from my mistakes.

i have the water meth hooked up at 5psi so that should be cooling the charge some what. and the car stiil makes boost normally but just makes the noise,
i will pull it off tommorrow and see if it has any fins left on the turbine

[delcowizzid]

trying to get it right??? the turbos is too small no point trying nothing LOL