Rev 3 Turbo Boost Cut

[Tonberry]

Speaking to an MR2 owner about his car and he mentioned the following;

Is this normal?

"You’ll find the drive/pull in the car (when you stick your foot fully down and leave it there) gradual at first, well sort off lol.. when the boost snaps in, which it will do fast at 3K (less than a second) the dash gauge will flick to max/off the scale, but then the Rev3+ ECU will compensate and back the boost off to around 0.8 bar hold for a second or so then back to max and the car will pull hard to 7K and won’t drop off due to rev3 camshafts. The ECU has control of the boost as I plumped the control vacume line back in as it allows the ECU to back of the boost even more in hot weather as it detects knock. When I brought the car this was disconnected, blocked off both ends at turbos actuator (can be done again if you wish, 10 minute job). If you nearly fully put your foot down the ECU will hold back the boost again around the 0.8 bar mark, you’ll feel it happen, but it won’t allow you to have full boost, not until you use 100% throttle. The Rev3+ ECUs control of boost stops the knock you nearly always get when boost suddenly changes from 0 to 1.1+ bar, especially if been sitting at traffic lights for ages and the engine bay gets hot, so as it is still silly quick I left the ECU in control as its protection. The cars intercooler is good enough for the feature to be disabled, as yes, if racing someone that 1 second hesitation on the boost might not be what you want, but I’d watch the boost in 26c + degree days if disabled."[/i]

[Peter Gidden]

Is this normal?

More like b0ll0x.

[Tonberry]

A little more detail would be appreciated.

[Driftlimits Performance]

Sorry for my friend Peters lack of detail.

He meant, that is complete dribble.

[Gullzter]

Speaking to an MR2 owner about his car and he mentioned the following;

Is this normal?

"You’ll find the drive/pull in the car (when you stick your foot fully down and leave it there) gradual at first, well sort off lol.. when the boost snaps in, which it will do fast at 3K (less than a second) the dash gauge will flick to max/off the scale, but then the Rev3+ ECU will compensate and back the boost off to around 0.8 bar hold for a second or so then back to max and the car will pull hard to 7K and won’t drop off due to rev3 camshafts. The ECU has control of the boost as I plumped the control vacume line back in as it allows the ECU to back of the boost even more in hot weather as it detects knock. When I brought the car this was disconnected, blocked off both ends at turbos actuator (can be done again if you wish, 10 minute job). If you nearly fully put your foot down the ECU will hold back the boost again around the 0.8 bar mark, you’ll feel it happen, but it won’t allow you to have full boost, not until you use 100% throttle. The Rev3+ ECUs control of boost stops the knock you nearly always get when boost suddenly changes from 0 to 1.1+ bar, especially if been sitting at traffic lights for ages and the engine bay gets hot, so as it is still silly quick I left the ECU in control as its protection. The cars intercooler is good enough for the feature to be disabled, as yes, if racing someone that 1 second hesitation on the boost might not be what you want, but I’d watch the boost in 26c + degree days if disabled."[/i]

[Tonberry]

Nothing to do with the ECU's TSVS?

[bobhatton]

Speaking to an MR2 owner about his car and he mentioned the following;

Is this normal?

"You’ll find the drive/pull in the car (when you stick your foot fully down and leave it there) gradual at first, well sort off lol.. when the boost snaps in, which it will do fast at 3K (less than a second) the dash gauge will flick to max/off the scale, but then the Rev3+ ECU will compensate and back the boost off to around 0.8 bar hold for a second or so then back to max and the car will pull hard to 7K and won’t drop off due to rev3 camshafts. The ECU has control of the boost as I plumped the control vacume line back in as it allows the ECU to back of the boost even more in hot weather as it detects knock. When I brought the car this was disconnected, blocked off both ends at turbos actuator (can be done again if you wish, 10 minute job). If you nearly fully put your foot down the ECU will hold back the boost again around the 0.8 bar mark, you’ll feel it happen, but it won’t allow you to have full boost, not until you use 100% throttle. The Rev3+ ECUs control of boost stops the knock you nearly always get when boost suddenly changes from 0 to 1.1+ bar, especially if been sitting at traffic lights for ages and the engine bay gets hot, so as it is still silly quick I left the ECU in control as its protection. The cars intercooler is good enough for the feature to be disabled, as yes, if racing someone that 1 second hesitation on the boost might not be what you want, but I’d watch the boost in 26c + degree days if disabled."[/i]

The ECU does control boost, timing, and fuel when it hears knock.
So with the stock boost control working the ECU can drop the boost if there is knock.
The fuel in Japan is a higher octane than we have here so the engines do run under the control of the knock sensor much more here.

By fitting a better intercooler or charge cooler you would have less knock but the best way is to fit lower compression pistons

[jimGTS]

this sounds like the guys is describing noticeable boost spikes??

the only reason you would feel what hes describing is if boost shoots to say 1.1bar, then comes back down to 0.8, then creeps again to say 1bar.
so can be sorted easily with a decent electronic boost controller.


this spike and creep is possible i guess with a decat and using the stock boost control system.



also reading between the lines hes saying he or someone fitted a boost controller to run higher boost than stock, and has now taken it off and returned to stock boost control.

[Tonberry]

Thanks guys.

He has fitted an electronic boost controller set to 1.1 BAR.

The engine has been rebuilt recently;

Full engine rebuild with new Toyota pistons/rings/main bearings and full gasket set (3 months ago/2000 miles) performed by myself, new Toyota ceramic stock turbo (no stupid race turbos or rebuilds with steal shafts so achieves full boost rapidly at 2800 RPM), fully ported/polished and skimmed cylinder head for increased power & flow (done by a head specialists in London), stock Toyota Rev3 camshafts and personally re-shimmed to within 0.01mm tolerance of the recommended Toyota clearances, so very quite head and better than standard.

[jimGTS]

any way to prove any of this rebuild??

why would anyone rebuild with oem pistons?

and theres NO WAY anyone would pay crazy money for a brand new oem turbo from toyota, probably would cost more than the cars value knowing toyota's parts department!

maybe it was just rebuilt to oem specs and is not new.


i would take all of these claims with a pinch of salt unless photographic proof.

[Draven]

I think last time a I checked a new CT20B from toyota was about £1750 or something like that.

[bobhatton]

Thanks guys.

He has fitted an electronic boost controller set to 1.1 BAR.

The engine has been rebuilt recently;

Full engine rebuild with new Toyota pistons/rings/main bearings and full gasket set (3 months ago/2000 miles) performed by myself, new Toyota ceramic stock turbo (no stupid race turbos or rebuilds with steal shafts so achieves full boost rapidly at 2800 RPM), fully ported/polished and skimmed cylinder head for increased power & flow (done by a head specialists in London), stock Toyota Rev3 camshafts and personally re-shimmed to within 0.01mm tolerance of the recommended Toyota clearances, so very quite head and better than standard.

The head should not have been skimmed as that will raise the compression ratio, totally the wrong way to go on a turbo engine.

[ashley]

Thanks guys.

He has fitted an electronic boost controller set to 1.1 BAR.

The engine has been rebuilt recently;

Full engine rebuild with new Toyota pistons/rings/main bearings and full gasket set (3 months ago/2000 miles) performed by myself, new Toyota ceramic stock turbo (no stupid race turbos or rebuilds with steal shafts so achieves full boost rapidly at 2800 RPM), fully ported/polished and skimmed cylinder head for increased power & flow (done by a head specialists in London), stock Toyota Rev3 camshafts and personally re-shimmed to within 0.01mm tolerance of the recommended Toyota clearances, so very quite head and better than standard.

If you are thinking of buying it, based on the info in this thread I would be walking away now...

[Tonberry]

Oh dear. Looks as if he may have made a pigs ear of things.

Did claim he has owned MR2s for 18 years and this was the best yet...