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Late secondary turbo?


Kol12

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I have never been overly impressed with the secondary turbo on my 99 Legacy TT. Mine does not kick in until 5000 RPM+ which usually means for over taking it comes in way to late... Apparently the spec is supposed to be 4000-4500 RPM kick in for the secondary turbo (Wikipedia). Is there any reason why mine would be triggering late like this? 

Edited by Kol12
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As above pretty normal. Should notice a period of lag and then at 5000rpm all of the fun starts to happen. Being year 99 version b/c will have a bit more of a slow/low boost compared to the last version they made. Is it auto or manual? My auto if you left your foot flat it will change to the next gear and be straight back into the power at 5000rpm was excellent for passing

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Ah so sounds about normal then. When passing I usually drop down from 4th to 3rd to get the rev's up quicker into the 4000-4500 range. It feels like it takes quite a bit of time to get from 4500 to 5000 rpm where the full boost kicks in, I have to push a bit, maybe this is the lag. It's usually about half way through the overtake that I'll hit boost, and nevertheless at that stage I'm off and usually always take the win!

 

It would be nice to have a bit of boost when launching into an overtake but I guess that's not how the TT is designed to work. Can't beat that low end boost of the TT though either. I have the 4 speed auto version so probably not as tuned as the manual. I pretty much always drive in manual mode which gives plenty of control.

Edited by Kol12
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Ah so sounds about normal then. When passing I usually drop down from 4th to 3rd to get the rev's up quicker into the 4000-4500 range. It feels like it takes quite a bit of time to get from 4500 to 5000 rpm where the full boost kicks in, I have to push a bit, maybe this is the lag. It's usually about half way through the overtake that I'll hit boost, and nevertheless at that stage I'm off and usually always take the win!
 
It would be nice to have a bit of boost when launching into an overtake but I guess that's not how the TT is designed to work. Can't beat that low end boost of the TT though either. I have the 4 speed auto version so probably not as tuned as the manual. I pretty much always drive in manual mode which gives plenty of control.

With the auto if I needed a quick pass and was doing 80 or under I would pop it in second with the we steering wheel shifter and then it would pretty much give me full boost when I went to pass as 80kmphr is about 4500 rpm in second. Then change third and lose your license if you don’t back off lol
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I have thought about changing down to 2nd to get primary turbo boost but I haven't been sure. If your in 4th gear travelling at 100 km (4th gear sits around 2500-3000 rpm I think?) would it be a bad idea to drop right back to 2nd gear? I know that if I am in 3rd gear hovering on 4000 rpm at 100 km the car does not like being dropped into 2nd at that speed, I'm not sure what the term is called, it's like the engine over revs. Do you know what I mean?

 

I'm thinking though that instead of dropping to 3rd from 4th to get the secondary turbo spooled up I could drop right back to 2nd and get the benefit of both turbos for an overtake? Since in 4th gear it's hovering very close around the primary turbo rpm (similar rpm to 2nd gear), dropping back to second shouldn't cause a sudden drop in rpm (as mentioned above) You would think you should be able to kick the primary up from in 4th gear but from what I remember I seemed to have some trouble with that. I've been using the 3rd gear and secondary turbo for so long maybe I should see again if I can get the primary to kick in in 4th gear for an overtake...

 

 

Edited by Kol12
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1 hour ago, Kol12 said:

I have thought about changing down to 2nd to get primary turbo boost but I haven't been sure. If your in 4th gear travelling at 100 km (4th gear sits around 2500-3000 rpm I think?) would it be a bad idea to drop right back to 2nd gear? I know that if I am in 3rd gear hovering on 4000 rpm at 100 km the car does not like being dropped into 2nd at that speed, I'm not sure what the term is called, it's like the engine over revs. Do you know what I mean?

 

I'm thinking though that instead of dropping to 3rd from 4th to get the secondary turbo spooled up I could drop right back to 2nd and get the benefit of both turbos for an overtake? Since in 4th gear it's hovering very close around the primary turbo rpm (similar rpm to 2nd gear), dropping back to second shouldn't cause a sudden drop in rpm (as mentioned above) You would think you should be able to kick the primary up from in 4th gear but from what I remember I seemed to have some trouble with that. I've been using the 3rd gear and secondary turbo for so long maybe I should see again if I can get the primary to kick in in 4th gear for an overtake...

 

 

 

 

I probably wouldnt drop it down to 2nd at 100km/h, but i regularly redline to every gear on a track day, think the end of 3rd gets me to 150km/h

 

Pretty sure you wont get the benefits of both turbos at the same time ever, iirc they come on seperately

 

Wouldnt it be perfectly set up so you can overtake in 5th? 5th gear at 100km/h should be around 3krpm which would be when the 1st turbo is at a nice power level?

if its auto just floor it when you want to overtake? the trans will no what to do

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Yeah it wont let you drop to 2nd at 100 will beep at you if you try to select it, that's if you have the sport shift anyway. pretty much I just drove it in auto and when I wanted to pass and keep it a short pass use sport shift as above otherwise if speed was above 80 I just had to wait for the transfer. People always bitch about the twin, and so on but I found once I new where the primary and secondary worked it was great. The worst thing was if you were trying to go full power and then you came off throttle while in high RPM so the secondary was boosting it would take awhile for the switch over to go back to the primary. Could have just been my car but then was like no boost for a good we period while it sorted its self out

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1 hour ago, THUNDA said:

 

 

I probably wouldnt drop it down to 2nd at 100km/h, but i regularly redline to every gear on a track day, think the end of 3rd gets me to 150km/h

 

Pretty sure you wont get the benefits of both turbos at the same time ever, iirc they come on seperately

 

Wouldnt it be perfectly set up so you can overtake in 5th? 5th gear at 100km/h should be around 3krpm which would be when the 1st turbo is at a nice power level?

if its auto just floor it when you want to overtake? the trans will no what to do

Primary boost is primary turbo (left side) only, secondary boost is both turbos together.

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1 hour ago, THUNDA said:

 

Wouldnt it be perfectly set up so you can overtake in 5th? 5th gear at 100km/h should be around 3krpm which would be when the 1st turbo is at a nice power level?

if its auto just floor it when you want to overtake? the trans will no what to do

99 auto is 4 speed, but yeah 4th gear drives around 2000-3000 rpm and it does get boost off the primary turbo. Maybe next time I will see if I can get primary turbo boost in 4th gear for an overtake. Like you say, this is probably the way it's setup to work... Whether you can go right through the rpm range and benefit from both turbos is another matter... I can see this thread turning into a how to drive a twin turbo, lol...

Edited by Kol12
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8 hours ago, duncanm said:

also check your ECV adjustment.

Check the ecv closes and seals first. Have seen many with worn pivot pins that don't close fully, causing exhaust leaks and a chattering valve.

6 hours ago, Kol12 said:

 

What exactly is the ECV? Is it the ECV rod adjustment your referring to?

I think someone needs to do some reading up on the twin turbo system and its operation. 

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1 hour ago, boostin said:

Check the ecv closes and seals first. Have seen many with worn pivot pins that don't close fully, causing exhaust leaks and a chattering valve.

I think someone needs to do some reading up on the twin turbo system and its operation. 

 

I have before but could do with a refresher. What does ECV stand for though?

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