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All top end on a tuned uk spec?


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Originally posted by Doughie

Branners

- what you wrote above almost exactly mirrors what my UK-spec car was like. The big kick came in about 4500-4800rpm when 2nd turbo came on-line properly. below that level it accelerated, but like you, it didn't feel that much different to stock performance below 4000rpm-ish.

 

Surely that would be normal as the boost on single turbo is being regulated by the by-pass circuit on turbo 2 until it comes on line.

 

Or does the blitz SBC-ID hook into the pre-spool circuit also????

 

If this is not the case you have to do something to stop the pre-spool from bleeding off boost (by pass or bleeder T)

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Guest Terry S

My hybrids #2 used to come in with a bang at 3800, which then changed to 4100 rpm with cams. Remember mine is a J spec. I think that's kinda normal for steel turbos but maybe I am wrong. You could tune some of this out with alterations to the timing but it would get expensive. Come on JB you've go a six speed now, there is no excuse ever to be off boost;)

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Right chaps. I thought I'd have a test in my Supra (And a last drive to drive it before it goes on Saturday) to see when it comes on boost etc after reading this thread. Obviously, I only did it for you guys.....wouldn't normally have put my foot down so much.

Anyway, my J-Spec.....accellerating in 2nd gear from 1500rpm, first turbo is in straight away at about 0.5bar....this stays boosting (Obviously) then at around the 4k mark the second turbo bangs in to life at about 0.85bar, after that obviously you can hold both turbos on boost quite happy.

My car still has CAT's, just has an after market exhaust from cats back.

 

So, sounds like my J-Spec is similar to JB's UK car.......maybe..??:confused:

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Also did a bit of experimentation today:

 

To reach .75 bar (max off no.1) took

 

from 3000rpm: 1.2secs

from 2500rpm: 1.8secs

from 2000rpm: 3.9secs

 

To reach .5bar on no.1 took

 

from 3000rpm: 0.6secs

from 2500rpm: 0.8secs

from 2000rpm: 1.5secs

from 1500rpm: 3.8secs

 

All tests were done in 6th gear, with a fully closed throttle, starting at -0.8bar. Timing was started the moment the throttle was touched.

 

Car is a full decat UK with bleed valve running Esso SUL.

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never really noticed how much boost you get on each turbo but it sure flys up fast when you boot it.

if i hold it steady at 3000rpm them do kick down it comes on power real fast am sure its before 4000rpm. not sure though. will have to check when i put car back together.

seems like forever since i have drove it now.

 

anyone fancy doing the ttc mod. am a bit unsure of loosing the quick spool up and getting a lot of lag.

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Originally posted by Matt Harwood

How DO you do that???

 

I can only get 0.7 on the first turbo :(

 

 

What can I say...she's a freak!! :D

 

I did the first turbo mod...ran 1bar at first but lost some response in the transition...so wound it back down to .9 ish :D

 

The first turbo mod requires

1 steel t-piece thumb screw bleed valve.

1 steel t-piece 4-6mm diameter both)

 

New rubber/silicone hose (about 30cm's to be safe...)

 

You weld the two t-pieces together on the | of the T's (or just join them with hose). Add hose to the other parts of the T and mount the lot by taking out the two vac hoses at the back left of the engine (right above the second turbo). There are 2 hoses that run right to left in parallel and bend down is a u-turn...your effectively linking the two pipes with your new contraption...put the bleed valve on the rearmost one. Wind it shut mark the shut point and open it half a turn...test.

 

IanC probably has pictures of his as we've both done it....

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I've been following this thread with particular interest as my car has been at Leon's this week having hybrids fitted.

As per my earlier post the car has always been a bit lacking in response lower down the rev range and after what Chris said I was a bit worried the new turbo's would make things worse.

However picked up the car yesterday and unless I'm mistaken it actually seems a fair bit better in that respect.

 

Mind you I was driving around in a 1.4 Corolla for a week!!

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Just to add to the bit about my UK having all top end, I set the record feature on the SBCID yesterday and watched what it did. It seems to get to about 0.77kg up to about 3500rpm, then do a drop to about 0.5 and then boosts up to 1 bar at about 4300rpm and 1.2 by about 5500rpm. This makes me think my prespool is messing about as I would have expected much less of a drop at transition. So thats the area Im going to get checked out unless anybody else has any thoughts.

 

JB

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Er, sorry folks, just the picture on it's doesn't cut it, then? I was in a hurry when I did the post :)

 

Right - ignore the rearmost blue hose. The two foremost hoses connect to a VSV. This VSV is closed when you are only using turbo #1. That means manifold pressure build up in the middle hose and the prespool valve gets pushed open the most boost that builds up - just like a normal wastegate. That's how #1 boost is controlled, and it also prespools #2 turbo.

 

The VSV opens up when you are using both turbos so the prespool valve shuts and both turbos operate through their normal plumbing.

 

The bleed valve releases manifold pressure past the VSV, in the same way a bleed valve works on a wastegate. It bleeds off into the exit hose from the VSV, so no air is lost to atmosphere and it remains a closed system.

 

The valve doesn't have to be opened much at all, 1/4 turns make a difference. Mine is set to 0.85bar at the moment. Makes 6th gear acceleration below 110mph better :)

 

-Ian

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Aha, but, my argument was that mine required no welding. Folks who want to cut up the t-piece and weld it onto the bleed valve can do so. Me, I went for the upgrade that required fingers and five minutes :)

 

Good question regarding the fuelling. I was running 0.7bar before the mod, and now 0.85, +/-about .03. Seeing as this is well within the MAP sensor's range I figure the ECU will compensate the fuelling naturally. The fuelling map must cater for increased boost on #1 turbo as there is no fuel cut system for it.

 

On top of this, under hi-throttle conditions I'm set to run safely rich anyway.

 

But, I haven't specifically had the fuelling checked on #1 running greater than stock boost. I'm not concerned, I think an increase of 0.2bar at low revs is easily taken care of.

 

-Ian

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