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The mkiv Supra Owners Club

low boost pressure


Hellstrom

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Hi.

 

The supra don't give full boost, should be 1.2bar and in sequential mode it gives around 0.9bars ive checked the valves and vacum hoses and haven't found any damaged one.

 

i tried going TTC mode and in ttc i only managed to get 0.45 bar of boost.. this seems strange. dunno what could cause this. No blue smoke i can hear the turbo/turbos spooling.

 

was thinking a split hoose buy why would i gain less pressure in ttc then? sounds strange.

 

any ideas?

 

it did make 1.2 bar like 2-3 days ago but there was a problem tho. at 6.500 rpm there was like a cut felt like a fuel cut. seems to only get that when pushing the trottle to 100% and in 6.5k rpm range. any ideas on this?

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ive resolved the boost now. was me that was stupid when i was on the boat i fiddled with the BC and somehow i managed to reset it when trying to fight my way back to the starting menu. so thats fixed. however the engine still cuts off when at aprox 6.5k rpm in 3:ed gear, might be the othergears aswell but haven't had enough road to actually test the other gears. 3:ed gear is the first gear also that gets full boost pressure. 2:ed gear only gets around 1.13bar and the full 1.2bar on 3:ed gear. and then a cut at around 6k rpm. any ideas?

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6500rpm? The rev limiter's only 300rpm higher at 6800rpm, are you sure it's not that? Your power's going to be sapping off before 6500 rpm on stock turbos anyway there's not much point in revving that high.

 

In my experience it is normal to get slightly higher boost in higher gears.

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Hard to tell really, iam thinking that it might be a FCD myself, well it revs beyound 6.5k on second gear atleast, and iam 100% confident its not the rpm limiter. well i guess i need to check if there is a FCD installed. the person that owned the car before John did have an Apexi FC controller hence there would be no use for a FCD in that system. he removed that one an put the original ECU back in place so iam thinking there might be no FCD. the "check engine" lights up and then goes back to normal after a few sec. ive checked the cods aswell and they say its code 35. and it adresses it to MAP sensor. i guess that could verry well be the ECU thinking its overboosting.

 

since its only really in 3:ed gear and beyond you get max boost pressure.

 

/hellström

Edited by Hellstrom (see edit history)
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well you don't get max pressure if you dont have the time to build it up, ie hitting the rev limiter too fast. well RPM is used to get a wider band of power, as you say its not having max power at thoose rpm but its not that much less either. my mk3 supra i had the limiter on 7.5k rpm with the cams i used in the engine is by far not the optimal operation rpm, but i got alot wider powerband. might not be nessesary with the stock twins since they build pressure fast enough anyway. but there is still something dodgy about it cutting off.

 

6500rpm? The rev limiter's only 300rpm higher at 6800rpm, are you sure it's not that? Your power's going to be sapping off before 6500 rpm on stock turbos anyway there's not much point in revving that high.

 

In my experience it is normal to get slightly higher boost in higher gears.

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