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Boosting too low?


Guest Stevo82

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Guest Stevo82

Hi, I just bought my first 1993 MKIV. I bought it from a guy 2 weeks after he bought it from a guy who bought it from the guy who imported it. :D

Well the guy I bought it from raced a BMW 135i 2 days after he bought it, and the Supra was absolutely destroyed by the BMW, seriously, after a few seconds the BMW was probably more than 50m in front of the supra,

they raced twice and it was the same both times. The BMW is supposedly stock, the guys had just bought it for his wife a few weeks earlier. I offered to buy the Supra from him after the race, he was pretty disgusted so I took my chance and it paid. I've always wanted a Supra.

 

Anyways, I am not sure what mods have been done except for fmic, cone filter, a manual boost controller which I dont know if its working ( coz its not closed but my boost is very low ) and a switch to go between

sequential and ttc. I've been reading a lot about all this so I have some questions. ( Oh and it was a n/a, but they put in a tt engine, still has the 5 speed gearbox, but a lsd was also fitted, think they said it has the

stock tt ecu )

 

I cant really find an answer to whether the boost spike on ttc will damage my turbos? It spikes to around 1.2bar but immediately drops back to 0.6bar.

 

Also, it seems stock boost is around 0.8 bar, is this correct? Mine only boosts 0.6 to 0.65 bar, can you think of reasons why?

 

I have a couple of other small issues (odo not always working, lights up but doesnt count, sometimes pressing the immobilizer button a couple of times makes it work, and the driver electric window doesnt work well, only

sometimes work in small increments, most of the time not at all, very irritating to have to open the door if you pay parking etc), but I'll still look around a bit.

 

I'll appreciate any comments you on the above!

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I would take the car to an auto electrician bud, that thing is a bonfire waiting to happen given all the electronic goings on you have. Sounds like things are shorting out left right and centre. It really isn't something people can comment on without seeing the wiring and being able to see what is going on.

 

I would personally take out the ETTC mod as I wouldn't want to rely on someone elses work, especially considering the bodge work that seems to be going on already. If you want to have the ETTC mod then fine, just get someone who knows what they are doing to do it properly with all the correct methods of splicing.

 

As for the boost it could be down to a few things. First thing to check for is boost leaks, be sure to check every coupling there is for splits or loose joins. Do the same with the vac lines, check every single one (PITA) to make sure they are not split and that they are on correctly, take your time as some can be hard to see properly, you need to check all the way around them.

 

Does the car still have the stock cats in place? Stock exhaust? If it has a double decat and an aftermarket exhaust I would look to see if there is a restrictor ring in place. If there is.. measure it and report back.

 

If you're still at a loss remove the turbo pipes from the front turbo and have a look at the blades on the tubby. If they are gubbed then that could explain why you are seeing low boost levels.

 

You should be seeing around 0.6-0.7bar on the 1st turbo and 0.7-0.8 when both come in (around 4krpm).

 

What boost gauge are you using? Where is it taking its feed from?

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Just to add. When you are driving the car, do you feel a sudden pickup around the 4k RPM mark? When the 2nd turbo comes online you should feel a power surge. If you aren't then it would suggest the 2nd turbo isnt coming online. The 1st turbo is then left to do all the work and will run out of puff soon after, making it read 0.6bar but feeling very sluggish.

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Guest Stevo82

Thanks for the advice. In sequential mode there is a surge when the second turbo comes in so I think both turbo's work. I've only had the car for 2 weeks and I've been very busy so I haven't had time to get to know the car. I'm

actually shocked about how little I know about my own car so I try to learn something every day. I also have a Starlet GT and I know the ins and outs of it, I do all of the work on it myself, but the Supra I'm not sure I'll try that just

yet, and I don't really trust anyone I know in Namibia to work on the car. I'm going to try to go through everything you mentioned this weekend and go from there. The boost gauge make is AutoGauge. Have no idea whats been done

with the exhaust system, will have to check.

 

In general, is a fuel consumption of 5km/litre normal, this is under moderate driving in the city? Driven hard I get around 3km/litre!

 

I was looking at the pics of your car just yesterday, and I must say, it might just be the best looking Supra I've ever seen! Made me decide to go black as soon as I can afford it, currently mine is a very flashy metallic orange!

 

Thanks again!

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I think that works out about 15mpg (UK Gallons). That isn't unheard of but it does seem low. Are you driving really short distances? If so then it's probably about right, if you are doing longer 60mph (100kmph) driving then you should be into the low 20s.

 

The most obvious reason for this would be the O2 sensor. They are quite pricey but a must have in order to have the car running well as it will be silly rich and down on power with a broken O2 sensor.

 

Thanks for the comments on my car, black is the best colour to have IMO but it is an absolute PITA to keep clean and doesn't look good when it isn't clean.

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Guest Stevo82

Under Hood Vacuum Lines forum1.jpg

 

This is how my boost controller is connected (by previous owner), I have adjusted it but it doesn't seem to make a difference. I don't understand the logic behind this installation. What do you think?

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Guest Stevo82

Yeah I thought so too but I just can't get to the vacuum pipes at the back of the engine, no space, and that's why I don't know where the blue silicone pipe runs to. But I'll get to it eventually, will just leave everything be for the time

being until I have more time.

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Yeah I thought so too but I just can't get to the vacuum pipes at the back of the engine, no space, and that's why I don't know where the blue silicone pipe runs to. But I'll get to it eventually, will just leave everything be for the time

being until I have more time.

 

There shouldn't be anything near the back of the engine bud. It should be completely stock. If the boost controller is hooked up there then it's all wrong.

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Guest Stevo82

I spoke to the guy who installed the boost controller today, he said he did it after a lot of research and that the boost controller hooked up like it is should apparently have made the 2nd turbo spool earlier, but it didn't work.

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I spoke to the guy who installed the boost controller today, he said he did it after a lot of research and that the boost controller hooked up like it is should apparently have made the 2nd turbo spool earlier, but it didn't work.

 

 

If it's hooked up the way you say it is it's very wrong.

 

The only reason you would have anything going to the rear vac lines, as already mentioned, is to up the boost of the 1st turbo. There is no way for the lines back there to influence the overall boost pressure that the turbos make so it has been plumbed in wrong.

 

There is a website (max-boost) that explains how to do the method mentioned, it is only an ADDITIONAL modification to get some extra boost below 4krpm. Perhaps the person who fitted it mistakenly read this as being the best method of getting more boost from both of the turbos.

 

The best thing to do is remove all the bodge fittings that the previous owner has done and see where you end up. If you get around 0.7-0.8bar of boost when both are online then we're off to a good start. However, there doesn't seem to be a whole lot of interest from you in following the advice I am giving you so I'm quite frankly not going to bother giving you any more on the subject.

 

Good luck with it though :)

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Guest Stevo82

Sorry, I'm just too busy now to do anything about it. It isn't as simple as just taking the stuff he put on off and putting back the original ones though. I don't even know what is going on behind there, I can't see where the pipes go and

there isn't even enough space for me to put my hand in there, I tried to feel where the pipes go but couldn't. I'll have figure out how to get to the pipes first and then where what should go. If I have time I'll look at it again on Sunday.

Thx anyways.

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Read this

 

http://www.max-boost.co.uk/max-boost/supra/boosting_the_beast.htm

 

It sounds to me like he has fitted the controller to the ebv at the back of the engine, which does NOTHING to up the boost of turbo 2.

This will only work with control of the wastegate valve, which seems he hasn't done.

Follow Scotts advice, the link above shows you how to plumb it back to stock.

The Max Boost site tells you to fit a MANUAL boost controller to the EBV, where your current control is, and a manual/electronic to to wastgate valve, thereby controlling the presooling and boost of No2.

Edited by Supranature (see edit history)
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Guest Stevo82

Cool thx, thats exactly what he did, he just used a silicone hose to go to the pressure tank and kept the metal pipe on the actuator but blocked off the T that used to go to the pressure tank. But so far I can see it is done like that guide

says. Would this increase boost in ttc and sequential? I've adjusted it a couple of times with no result in ttc. This twin turbo thing is confusing. That guide also shows that I have to remove a couple of things to get to those pipes, I didn't

have time to do anything on Sunday, maybe this weekend though, also have to install my new suspension, but that'll have to wait until mid November methinks.

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