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Down on power, first turbo missing?


Fulcrum2000
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Hi All

 

So over the last couple of weeks I've noticed a small smell of petrol on WOT but no loss of power, and then this morning when I went to overtake it was like I had 'lag' and then the turbo kicked in.  I am wondering if the exhaust is a little loose or if for some reaosn the first turbo isn't kicking in?  on WOT later this morning it was significantly down on power overall but my BC is telling me I am getting pressure and the max is 1.12, any ideas?  

 

I'm TT 93.

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You need to be careful at higher revs and WOT incase the sequential system isn't working properly as sometimes it can overspeed/work the first turbo.

With no first turbo at all, it'll be sluggish at low rpm's? If you were overtaking it sounds like the lag may have been from the 2nd turbo transition and/or second turbo problem?

Switching to TTC for a bit can give some good info and will protect the first turbo

Look at the link and try and see if you have problem 1, 2, 3 or 4?

 

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1 hour ago, Fulcrum2000 said:

Yeah, the car only had a service 2 months ago, new plugs etc.  It's an Auto full BPU and has even had a full engine rebuild prior to the BPU and only done about 3000 miles since, all flawlessly.

When you say lag, was it misfiring? Reason I asked re drive train is because the autobox torque converters can get sluggish if low on fluid which gives 'lag' feeling. 

If it's engine related, do all the standard checks on vsv's, chuck into TTC mode, if problem persists, check for boost leaks, the old stock IC welds can fail which open up under pressure but look fine on idle. Another hose to check is the turbo link hose as they collapse internally and look fine at a glance. I have a replacement Whiftbitz if you need one. 

Could also be a sticking actuator, but I'd hazard a guess that you'll find the issue before you move onto that. 

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No misfires, when the first turbo kicks in it does seem to pull more but not massively, but BC and gauge are both reading pressure - the spool sound is definitely quieter on that though.  If carried on to WOT it then pulls at about half the rate of normal.  I will drive it more today and see if I can gauge more.  I would say it's running on one turbo but I can't figure out which one it is and obviously I am going to have to go a bit gingerly now.  The autobox oil is bang on and was replaced when the rebuild happened so should be tip top.

 

How do I put it into TTC?  I assumed this was much more involved and I never wanted TTC as I love the power band of twins but if it helps diagnostically I am happy to temporarily do it?

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7 hours ago, Fulcrum2000 said:

No misfires, when the first turbo kicks in it does seem to pull more but not massively, but BC and gauge are both reading pressure - the spool sound is definitely quieter on that though.  If carried on to WOT it then pulls at about half the rate of normal.  I will drive it more today and see if I can gauge more.  I would say it's running on one turbo but I can't figure out which one it is and obviously I am going to have to go a bit gingerly now.  The autobox oil is bang on and was replaced when the rebuild happened so should be tip top.

 

How do I put it into TTC?  I assumed this was much more involved and I never wanted TTC as I love the power band of twins but if it helps diagnostically I am happy to temporarily do it?

Give this guide a try to temporarily try TTC mode: http://mkiv.supras.org.nz/articles/andy.htm

 

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Thanks for your help guys.  Ok so I have driven it significantly more and it is the first turbo just not doing much, I can go along a road and whilst the boost gauges show pressure there is no increase in speed beyond engine power, ie its linear, until about 4000 or so when I suddenly get boost.  By this point I am doing 80 or so (I'm not on WOT) so I am assuming it is the second turbo.  The more I drive it the more 'puddingy' I've noticed it to be around town as well, which I am taking as a sign that it is NA until second turbo.  

I think switching it to TTC is a bit beyond me so I am going to book it in with the Jap car specialist and get them to resolve it as I would imagine it is just a blocked line or something as it's not pluming smoke etc.  

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27 minutes ago, Fulcrum2000 said:

Thanks for your help guys.  Ok so I have driven it significantly more and it is the first turbo just not doing much, I can go along a road and whilst the boost gauges show pressure there is no increase in speed beyond engine power, ie its linear, until about 4000 or so when I suddenly get boost.  By this point I am doing 80 or so (I'm not on WOT) so I am assuming it is the second turbo.  The more I drive it the more 'puddingy' I've noticed it to be around town as well, which I am taking as a sign that it is NA until second turbo.  

I think switching it to TTC is a bit beyond me so I am going to book it in with the Jap car specialist and get them to resolve it as I would imagine it is just a blocked line or something as it's not pluming smoke etc.  

Good call with booking it in with a specialist. Tbh, it could be a variety of things as per my other post. 

A decent garage who knows the cars will be able to elimate the issue in reasonable time. 👍

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Have you replaced the stock convoluted hoses on the intake side of the turbo's like in the pic below?

They can collapse inside restricting the intake flow but look fine from outside causing issues with boost, I had a similar problem when I was BPU 🙂

image.png.478fa1902912f7459609cd84257acc01.png

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Yes I've outwardly checked all hoses etc but thanks so much for this info I have passed it on to Rob at the Japanese car specialist where it is going next week.  It's defo turbo, its just like driving an NA at low speeds.

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I had a similar problem quite a few years back, when the second turbo wasn't coming on line, it turned out to be a sticky "Exhaust gas control valve", (EGCV) or it could be the EGC switch.  If you go to the Technical section and look in Technical Discussion, and then the first topic "Sequential Turbo" there are some really good info. You can actually put your hand down to the actuator  hold it and move it back and forward it should go reasonably easily.

Hope this may help, at least it will narrow down the things to consider.

Bob.

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