Clutch slip - (was Overboosting)

Here are the symptoms:

1st 2rd 3rd 4th is fine

5th and the 6th is where the problem lies, it seems like its over boosting. On those two gears the rev goes crazy and from 4000rpm when the second turbo comes on, only happens if im flooring it, but if i steadily press the pedal its fine.

I've spoken to a few member at the meet about it, just wanted to few more opinion.

i've been advised to get a new ECU if so it probably be the S6 but what im worried about its driving the supra, would i damage the cylinders? if i just use it for a drive and don't push so hard on the 5th and the 6th?

Oh yeah my set up is full BPU.

Sticky actuator maybe??

The revs go crazy? Sounds like your clutch is slipping bud.

The revs go crazy? Sounds like your clutch is slipping bud.

Was thinking that......lol unless its a typo error

The revs go crazy? Sounds like your clutch is slipping bud.

is there any way to find out if it is slipping?

What i describe is not overboosting ?

is there any way to find out if it is slipping?

 

What i describe is not overboosting ?

No, what you are describing is the cluch slipping.

Overboosting is where the boost spikes. Ie, you have it set for 1.2bar and it spikes to 1.4 bar.

Clutch slipping is where when you floor it the revs climb but the speed doesn't. The most likely time to notice clutch slippage is in the higher gears at peak torque, which is approx where you are seeing it.

No, what you are describing is the cluch slipping.

 

Overboosting is where the boost spikes. Ie, you have it set for 1.2bar and it spikes to 1.4 bar.

 

Clutch slipping is where when you floor it the revs climb but the speed doesn't. The most likely time to notice clutch slippage is in the higher gears at peak torque, which is approx where you are seeing it.

okay, so i guess time to replace with a new and better clutch? would you recommend a clutch to use?

I'm pretty sure a stock clutch is fine for BPU. I've been running a stock clutch since I got the car and never had any issues.

If you're thinking of a single turbo in the future then it might be a good idea to upgrade. It's a minefield though, I went with the RPS Twin Carbon/Carbon clutch. At approx 2k shipped it's not cheap though.

I'm pretty sure a stock clutch is fine for BPU. I've been running a stock clutch since I got the car and never had any issues.

 

If you're thinking of a single turbo in the future then it might be a good idea to upgrade. It's a minefield though, I went with the RPS Twin Carbon/Carbon clutch. At approx 2k shipped it's not cheap though.

Is it safe to drive, i mean for the engine. I'm not going to blow the cylinders or anything?

2k shipping.... maybe a little more saving up i guess then buy this clutch, gona bookmark it for now. Strange that my is a stock clutch and its doing that on a BPU, could there be any other reasons for the rev to spike like that?

 

Is it safe to drive, i mean for the engine. I'm not going to blow the cylinders or anything?

It isn't 2k for the shipping, it's 2k for the clutch AND shipping... ie 2K shipped

The reason it's doing it is the clutch has worn. Clutches wear, and they need replaced. It just so happens that yours is coming to the end of its life. If you replaced it with a new stock clutch it would be fine. No other reasons I can think of for it spiking, I'm positive it's a slipping clutch.

Perfectly safe to drive, try not to let it slip too much as you will only cause it to wear faster and faster until you end up with no friction surface left at all.

Try pulling away in 3rd or 4th and it should stall pretty quick, if its slipping bad you wont go too far and the revs will increase. ie. no power transfer. Normally a good indicator, but dont go mad with this giving it loads of revs as you do not want to break anything.

I have a stock 6 speed clutch for sale if interested mate, coped with 420bhp no problem

Mine was doing this when I bought it, as Scott said it was the clutch. Down to the fact that more power was being produced in higher gears it was only noticeable when booting it a little in 4th but mainly 5th and 6th. If you keep slipping it without changing the clutch you will also wear the flywheel out. Tbh, it's a good idea to change both of them at the same time - with parts and labour you will be looking at around £1k, maybe a little less.

Put it in 5th at about 30-40mph then put your foot down and the revs should rise but the speed shouldn't (too much). Good indication if it's just the clutch slipping.

Thanks for the info guys. I might go and have a drive to see how bad it is then decide on how quick I replace the clutch. Like you said scott, I'm planning to go single so might as well buy a better set up.

I do an uprated stock clutch, please see below:

I use the stock, brand new driven plate, as it is correctly

balanced, doesn't judder and will hold all but mega torque

highly modded engines or cars used for drag racing.

I modify a stock brand new cover to give more clamping force.

The reason I tooled up to do these is some of the aftermarket

US clutches I have fitted SEEM to be built from used cover

assemblies with reground friction surfaces, and a stronger

spring. I have had hellish trouble getting these to fully

release, because due to this seemingly thinner cast iron

friction face, the geometry of the clutch goes to pot, and

being a pull type clutch (the hydraulics pull the bearing

away from the engine, rather than the more normal push type)

it is a lot harder to effect a cure.

For 455 pounds plus VAT , you get a brand new driven

plate, a brand new modded cover, and a brand new release

bearing. I would rather fit myself so any complaints are down

to me, I see a lot of clutches damaged by people without the right gear

(a ramp and transmission jack, plus correct circlip tools and fitment)

or clutches fitted to patently *uggered flywheels. I will do a supply

only if you feel competent to tackle the job or are using a bona fide garage to

fit the clutch

Toyota use a dual mass flywheel (the flywheel is in 2 parts, an inner and

outer assembly, damped in the middle) which is now showing signs

of wear causing a lot of rattle when idling or on very light

throttle openings. For God knows what reason they are charging

about £400 + VAT for a new one, they look more like they should be

over 500 to me, but don't say anything :-) The very similar LUK dual

mass flywheel on Maseratis is nearly £1000 + VAT.... So if the flywheels

old enough or abused enough to be scored it should be replaced.

Fitting by myself will cost £175 + VAT.

Reply privately if interested please. [email protected]

How much power could this clutch hold up to? Because I be planning to go single next year. Your prices are similar to whifbitz clutch which I have looked at, if not yours might cost less. But I just want to make sure these can handle more than stock ones.

Clutches are rated in torque, anyone advertising a clutch capable of X BHP is just showing they have no idea about drive line component ratings or how they work. It's a pet hate of mine. It is designed to handle about 20% more torque than stock, but people have run 30% and had no real issues, although I wouldn't recommend it. So about 390 to 400 ft lbs of torque.

Clutches are rated in torque, anyone advertising a clutch capable of X BHP is just showing they have no idea about drive line component ratings or how they work. It's a pet hate of mine. It is designed to handle about 20% more torque than stock, but people have run 30% and had no real issues, although I wouldn't recommend it. So about 390 to 400 ft lbs of torque.

Would I not be right in saying that the stock clutch would be designed to handle a fair bit more than stock? I have the stock clutch and it handled BPU power with no issues or dramas whatsoever (Estimated to be around 400ft lbs). Your re-designed clutch would surely handle 20% more than the stock clutch rather than 20% more than the stock torque figure?

Atock is designed to have a long life even with ham footed usage in all condition, so it will have some overhead at the risk of reduced life. Mine has more clamping pressure and should be good for +20% torque. Obviously be retaining the stock architecture torque handling has to be balanced against life and pedal pressures, and what the stock release mechanism is happy to pull. Your bits should be with you tomorrow, with brake caliper pins following shortly, some idiot sent me 5mm rod instead of 6 mm and I only noticed when i got it out of the packing, sorry.

Atock is designed to have a long life even with ham footed usage in all condition, so it will have some overhead at the risk of reduced life. Mine has more clamping pressure and should be good for +20% torque. Obviously be retaining the stock architecture torque handling has to be balanced against life and pedal pressures, and what the stock release mechanism is happy to pull. Your bits should be with you tomorrow, with brake caliper pins following shortly, some idiot sent me 5mm rod instead of 6 mm and I only noticed when i got it out of the packing, sorry.

Just making sure you aren't under-selling your clutch

No worries mate, replacing the pins can be done at any time. Injectors all good then?

/hijack

Yes, all well in tolerance, but I have to say I don't like drilled injectors myself, prefer OE ones of he size they were designed to be.

A lot depends on how a clutch is used as to how long it lasts, of course, I am very gentle on them, and never do any racing starts, except when I am, err, racing, IYSWIM?

Drag racing basically kills everything though

Clutches are rated in torque, anyone advertising a clutch capable of X BHP is just showing they have no idea about drive line component ratings or how they work. It's a pet hate of mine. It is designed to handle about 20% more torque than stock, but people have run 30% and had no real issues, although I wouldn't recommend it. So about 390 to 400 ft lbs of torque.

with 390 to 400ft lbs of torque, if that is true, im only guessing and looking online for more information it should handle a supra with about 500BHP. I know your pet hate is people talking about bhp for clutches, but it would help to give me a idea because if i was to change the clutch i might as well get uprated one for later when i change the turbo to reach arond 500BHP+

Hi all,

Recently I've been having the problem as well that my clutch is slipping in 5th and 6th when flooring it. Now my Supra TT has done just over 90.000 Km (kilometers! so almost 60.000 miles).

My question is whether or not this is a normal number of miles for the stock clutch to be worn out? (of course depends on driving style, but don't own it very long so don't really know)

Supra has very little mods engine wise, only open air filter and boost controller with stock jap twins (14 psi / 1 bar).

Yes, about right for a TT clutch, although I have seen people get more (and a LOT LOT less ) If it interests you I now offer a standard OE Toyota clutch modded with higher clamping force, so will take modest torque incresess in its stride, and offers no discernible increase in pedal pressure, zero judder and totally smooth operation. Please see below for details.

I use the stock, brand new driven plate, as it is correctly

balanced, doesn't judder and will hold all but mega torque

highly modded engines or cars used for drag racing.

I modify a stock brand new cover to give more clamping force.

The reason I tooled up to do these is some of the aftermarket

US clutches I have fitted SEEM to be built from used cover

assemblies with reground friction surfaces, and a stronger

spring. I have had hellish trouble getting these to fully

release, because due to this seemingly thinner cast iron

friction face, the geometry of the clutch goes to pot, and

being a pull type clutch (the hydraulics pull the bearing

away from the engine, rather than the more normal push type)

it is a lot harder to effect a cure.

For 455 pounds plus VAT , you get a brand new driven

plate, a brand new modded cover, and a brand new release

bearing. I would rather fit myself so any complaints are down

to me, I see a lot of clutches damaged by people without the right gear

(a ramp and transmission jack, plus correct circlip tools and fitment)

or clutches fitted to patently *uggered flywheels. I will do a supply

only if you feel competent to tackle the job or are using a bona fide garage to

fit the clutch

Toyota use a dual mass flywheel (the flywheel is in 2 parts, an inner and

outer assembly, damped in the middle) which is now showing signs

of wear causing a lot of rattle when idling or on very light

throttle openings. For God knows what reason they are charging

about £400 + VAT for a new one, they look more like they should be

over 500 to me, but don't say anything :-) The very similar LUK dual

mass flywheel on Maseratis is nearly £1000 + VAT.... So if the flywheels

old enough or abused enough to be scored it should be replaced.

Fitting by myself will cost £175 + VAT.

Reply privately if interested please. [email protected]

Thanks.