Two stage boost - GT-R Register - Official Nissan Skyline and GTR Owners Club forum

Gidders · 23rd August 2005, 09:53 AM

sorry, stuck the post in the wrong area

Guys,
Just got my R33 GTR, something I have noticed is that she only pulls about .7/.8 bar until 5k rpm then she will go upto 1 bar and its like a third turbo kicks in and all hell breaks loose !
I know about two stage boost, but I have a blitz boost controller which I thought would over ride this ? keep a constant maximum boost through the rev range ?
I dont think it is lag as she spools up into positive boost under 2k rpm and .5 by 2-3k rpm hard to get exact figures as im normally trying to keep one eye on the horizon and the other on the rev/boost gauges. With the light fly wheel revs do pick up quickly.
Just seems odd that she feels not much quicker than my 300 bhp scooby until 5k and then she feels like a Maclaren F1? is this right do all GTR's go like this ? If so, its goona hurt my wallet driving everywhere at 5k to have some fun ?

mattb · 23rd August 2005, 10:05 AM

As far as I know the GTR does not have two stage boost nor should it have and variable valve timing. GTRs are known to be a bit lack lustre before they come on boost.

I think perhaps there are two options, the first is down to your map the second is your turbos. The car may have been mapped for easy driving as opposed to all out speed at lower revs. The second could be that you have either a problem with your turbos boosting or they are aftermarket and taking a bit of time to spool up.

It might be worth going to a meet and sitting in someone elses to see if it is just you or there is something up with the car.

Gidders · 24th August 2005, 11:12 AM

I was under the impression it did have variable valve timing ? not to sure on the boost as it is controlled by the ECU ?
I do remember test driving a few skylines a while ago and they all seemed to really pull as the rev's increased. From 5k upwards. Even into the red line they were very strong which I thought was unusual for a turbo'd car as tourque from a 4 cylinder has run out by the red line. I dont think there is a problem with the turbo as it does eventually reach maximum boost and it spools up very quickly to .7 or so, then just seems to wait until 5k before going the whole hog ? I think your idea of the ECU being setup this way may be the answer ? I am off to Abbey in a few weeks so the dyno should explain all.

cheers

lightspeed · 24th August 2005, 11:42 AM

If the Blitz boost controller is linked to the optional Blitz MAP analyser then Blitz dealers can map the boost versus rpm in each gear.

What's the rest of the spec?

Gidders · 24th August 2005, 01:50 PM

long list; but these are just the engine mods

HKS twin induction
blitz dual solenoid boost controller
arc intercooler/radiator
R34 turbos
oil/fuel pump and catch tank
torgue split convertor (which I have not really had time to play with yet)
ECU has been re-mapped, not sure how exactly ? need abbey to confirm
Apexi N1 exhaust system with high flow cat.
light fly wheel with twin plate clutch

As I say she really pulls from 5k upwards, still quick below and the fly wheel defo helps the initial acceleration, well into positive boost by a few thousand revs and I have a warning set on the boost controller for .6 bar and this starts flashing and beeping by 3k rpm. At 5k the boost does increase by say .2 bar, but the additional push from the engine feels more like 1 bar, it really is noticable quicker feels like a extra 100 bhp where as the extra .2 bar is only gonna give me say 20 or 30 bhp ? its strange. I think the engine must be mapped for certain boost and fuel/air etc at different points during the rev range ? Hoping the dyno will shed some light ?

cheers

kingsley · 24th August 2005, 06:00 PM

As I posted in the other topic ...

When I had a broken inline air filter that fed the boost pressure sensor (as used by my boost controller), it behaved exactly as you describe. In my case the boost controller wasn't seeing boost and so wasn't triggering the control solenoid. Is your boost control solenoid working?

I would have expected it to stick to about .6 bar up to 8000rpm but because of the other tuning my engine has had, I don't think the stock wastegates (I've got R34 turbos too) can keep the boost that low at high rpm. I could be wrong but it seems to make sense. I get the same behaviour if I turn off the boost controller completely.

23rd August 2005, 09:53 AM	#1 (permalink)
Gidders GTR Register Member Join Date: May 2005 Location: Reading, UK Posts: 98	Two stage boost sorry, stuck the post in the wrong area Guys, Just got my R33 GTR, something I have noticed is that she only pulls about .7/.8 bar until 5k rpm then she will go upto 1 bar and its like a third turbo kicks in and all hell breaks loose ! I know about two stage boost, but I have a blitz boost controller which I thought would over ride this ? keep a constant maximum boost through the rev range ? I dont think it is lag as she spools up into positive boost under 2k rpm and .5 by 2-3k rpm hard to get exact figures as im normally trying to keep one eye on the horizon and the other on the rev/boost gauges. With the light fly wheel revs do pick up quickly. Just seems odd that she feels not much quicker than my 300 bhp scooby until 5k and then she feels like a Maclaren F1? is this right do all GTR's go like this ? If so, its goona hurt my wallet driving everywhere at 5k to have some fun ?

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23rd August 2005, 10:05 AM	#2 (permalink)
mattb GTR Register Member Join Date: Feb 2002 Location: Milton Keynes Posts: 1,416	As far as I know the GTR does not have two stage boost nor should it have and variable valve timing. GTRs are known to be a bit lack lustre before they come on boost. I think perhaps there are two options, the first is down to your map the second is your turbos. The car may have been mapped for easy driving as opposed to all out speed at lower revs. The second could be that you have either a problem with your turbos boosting or they are aftermarket and taking a bit of time to spool up. It might be worth going to a meet and sitting in someone elses to see if it is just you or there is something up with the car.

24th August 2005, 11:12 AM	#3 (permalink)
Gidders GTR Register Member Join Date: May 2005 Location: Reading, UK Posts: 98	I was under the impression it did have variable valve timing ? not to sure on the boost as it is controlled by the ECU ? I do remember test driving a few skylines a while ago and they all seemed to really pull as the rev's increased. From 5k upwards. Even into the red line they were very strong which I thought was unusual for a turbo'd car as tourque from a 4 cylinder has run out by the red line. I dont think there is a problem with the turbo as it does eventually reach maximum boost and it spools up very quickly to .7 or so, then just seems to wait until 5k before going the whole hog ? I think your idea of the ECU being setup this way may be the answer ? I am off to Abbey in a few weeks so the dyno should explain all. cheers

24th August 2005, 11:42 AM	#4 (permalink)
lightspeed GTROC Member Join Date: Jul 2002 Location: South-west Posts: 1,812	If the Blitz boost controller is linked to the optional Blitz MAP analyser then Blitz dealers can map the boost versus rpm in each gear. What's the rest of the spec?

24th August 2005, 01:50 PM	#5 (permalink)
Gidders GTR Register Member Join Date: May 2005 Location: Reading, UK Posts: 98	long list; but these are just the engine mods HKS twin induction blitz dual solenoid boost controller arc intercooler/radiator R34 turbos oil/fuel pump and catch tank torgue split convertor (which I have not really had time to play with yet) ECU has been re-mapped, not sure how exactly ? need abbey to confirm Apexi N1 exhaust system with high flow cat. light fly wheel with twin plate clutch As I say she really pulls from 5k upwards, still quick below and the fly wheel defo helps the initial acceleration, well into positive boost by a few thousand revs and I have a warning set on the boost controller for .6 bar and this starts flashing and beeping by 3k rpm. At 5k the boost does increase by say .2 bar, but the additional push from the engine feels more like 1 bar, it really is noticable quicker feels like a extra 100 bhp where as the extra .2 bar is only gonna give me say 20 or 30 bhp ? its strange. I think the engine must be mapped for certain boost and fuel/air etc at different points during the rev range ? Hoping the dyno will shed some light ? cheers

24th August 2005, 06:00 PM	#6 (permalink)
kingsley GTR Register Member Join Date: Aug 2002 Location: West Surrey Posts: 1,801	As I posted in the other topic ... When I had a broken inline air filter that fed the boost pressure sensor (as used by my boost controller), it behaved exactly as you describe. In my case the boost controller wasn't seeing boost and so wasn't triggering the control solenoid. Is your boost control solenoid working? I would have expected it to stick to about .6 bar up to 8000rpm but because of the other tuning my engine has had, I don't think the stock wastegates (I've got R34 turbos too) can keep the boost that low at high rpm. I could be wrong but it seems to make sense. I get the same behaviour if I turn off the boost controller completely.