zircon
Part of things
Posts: 327
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Jun 15, 2012 12:17:56 GMT
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Afternoon fellas.
Hopefully you can help me resolve a problem that I have been putting up with in my 1993 MR2 for some time now - that is really worrying me and ruining the driving experience.
My car is modified, with the standard 2 litre N/A engine swapped out for a 2 litre Turbocharged MR2 engine from an imported car.
Other relevant modifications to the chassis are:
1/ Uprated front Anti-roll bar
2/ Front and rear strut tower braces
3/ Lower chassis brace at the front
4/ Coilover suspension lowering the car approximately 35-45mm
5/ Brake upgrades (detailed below)
Before the conversion was undertaken my brakes felt fine and confidence inspiring. However, ever since the conversion I have felt the brakes have been seriously lacking in potency.
My initial thoughts were that the brakes were struggling with the new power (125bhp increase), but thinking about it, braking from say 50mph is the same whatever engine you have (so long as there is no weight difference or positioning between engines (which there is not). Furthermore, my car shares the same revised brake setup (Factory revision 2 changes) as designed by Toyota: 2 pot fronts and 1 pot rears with larger diameter discs and bigger calipers than when the Mk2 MR2 was launched. Therefore the brakes should be adequate (and I often read that they are actually a strong set-up for the car).
I was running blueprint consumable parts and decided to upgrade in order to cure the issue:
1/ Grooved Gold Zinc plated CRN discs
2/ EBC Yellow Stuff Pads
3/ Goodrich Braided brake hoses
4/ Motul RBF 600 fluid (bled properly)
5/ Brake booster 'stopper' brace
6/ Pair of reconditioned front calipers
7/ All calipers overhauled with new sliders, rubber slider boots, ceramic grease etc.
The improvement was apparent, but only a little better than it used to be, however if I brake I am still wincing at how slowly it pulls up from cruising at say 50mph.
The car has been through various MOT brake tests without any faults logged.
I have done the brake booster test for operation and it folllows factory behaviour. I have also checked the 1 way valve from the engine vacuum port and associated rubber tubing for splits.
I drive a 2001 BMW 325Ci as a daily which has great brakes and feel much more confidence inspiring. Previously I was driving a 1995 BMW 318is and before that a Toyota Celica from 1994 - these also felt confidence inspiring.
Lots of others on the MR2 Owners club have had engine conversions and nobody complains of the same problem.
I have recently read articles on other non-Toyota websites about cars being lowered and this affecting the brake balance unit which thinks that there is extra weight in the back and compensating the balance to deal with this. Is this likely to be a consideration?
One final thought is that the car is in need of a good laser alignment after I put the current coilovers on, but the issue was still there with teh previous coilover setup where the car handled well on its alignment.
Any suggestions / input would be gratefully received.
Rob
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Last Edit: Jun 16, 2012 13:50:25 GMT by zircon
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mk2cossie
Club Retro Rides Member
Posts: 3,063 
Club RR Member Number: 77
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Jun 15, 2012 12:31:48 GMT
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as you say its all later spec MR2 bakes, is the master cylinder the same for all models? if the revision brakes have a diferent size bore master cylinder, that will cause un nerving brakes due to the pedal having more travel  if theres a load valve on the rear suspnsion arm, try it with it set to a more factory position, they usually have an adjustment on them ;D oh, and if it is a load valve (or whatever toyota call it), get some one to pump the brake pedal and check the arm on the valve pulses with the pedal presses  |
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RobinJI
Posted a lot
"Driven by the irony that only being shackled to the road could ever I be free"
Posts: 2,995
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Jun 15, 2012 12:38:31 GMT
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Was the master cylinder revised at the same time as the calipers? If it's size is wrong then you may find them lacking power. I take it the problem is how much pressure you have to put on the pedal?
How do they feel? Do they feel as solid or spongy as expected for the car? Importantly, have you driven another MR2 which should have a similar set-up for comparison? or at least felt the brake pedals firmness?
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Jun 15, 2012 12:44:48 GMT
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Aren't YellowStuff full race-spec pads?
They're probably just not getting up to proper operating temperature.
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oooooh I'm so badass.... I've got a z in my name  |
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Jun 15, 2012 12:50:56 GMT
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I've got a rev1 with the upgrade to rev2 brakes and it brakes fine.
Ensure there bled correctly ABS can cause a right ballache when bleeding, also I'd ditch thge yellow stuff pads and put OE ones back in.
Mine has always been fine even hauling its ass to a stop from 140 MPH at Rockingham.
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Some days you just need to take a grinder to an inanimate object, just to make your day a tiny bit better!!
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sparkyt
Posted a lot
selling stuff
Posts: 1,767
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Jun 15, 2012 12:51:30 GMT
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Don't use hi spec pads for the road you'll need a lower operating temp other than as pointed out by others . It could be the size of the master cylinder is the piston the same size on the old and new callipers
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Jun 15, 2012 15:54:26 GMT
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Agreed with the others, I'd ditch the pads first for some decent road rated ones (as mentioned, stock Toyota ones should be up to the job). I had no end of problems with EBC pads on one of my previous cars giving poor braking (lack of bite and feel). I changed them for some Ferrodo pads and the braking improved massively right from the outset, even before they were properly bedded in. The difference was immense.
As also mentioned, try re-bleeding the system again going through the procedure recommended by Toyota.
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bortaf
Posted a lot
Posts: 4,549
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Jun 15, 2012 19:45:21 GMT
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I have had turbo conversions in where the brakes have suddenly felt very hard, it was cos turbo cars use a one way valve in the servo line to hold the vacume when on boost (obv no vacume when on boost), did you change this to the new setup? it might be a differant spec to the NA version?
Thta is IF the problem is a hard pedal/low clamping force ??
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R.I.P photobucket
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Jun 15, 2012 19:55:34 GMT
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I used to run EBC yellow pads on my seat rally car they were ok when cold but obviously far better when warm they are as everyone has pointed out a high spec comp pad.EBC greens are a better bet for road use.I think as others have pointed out a master cyl or abs bleeding problem
Dave
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Jun 15, 2012 23:34:26 GMT
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Extra heat from the turbo cooking the fluid somewhere?
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Volvo back as my main squeeze, more boost and some interior goodies on the way.
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zircon
Part of things
Posts: 327
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Jun 16, 2012 13:49:16 GMT
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Thanks for the reply - the master cylinder is the correct one for the system, I haven't upgraded the actual braking system, and this is as it came from factory, I was just mentioning that it has the better of the 2 systems that were fitted to the MR2.
Pedal feels firm and the system has been properly bled.
I was informed when getting the ebc yellows that they were fast road pads with good bite from cold. Regardless the problem was there before changing pads when it was on stock pads.
The car is a non-abs version.
Problem definitely seems to be hard pedal and low clamping force, I will check out the 1-way valve and balance valve,
Cheers.
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Jun 16, 2012 15:57:13 GMT
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My Dad's MGB had EBC Greenstuff pads in it when he bought it. Despite being the mildest ones in the EBC range, there was no bite at all. I've had a similar experience with cheap 'standard' linings in my car - little bite - but these faded early too. Swapping to some quality standard pads (Mintex on both IIRC) brought back the bite.
I'd run good quality branded standard pads, and only upgrade to something with a bit more heat tolerance if you experience lining-induced brake fade (rigid pedal and little braking - boiling fluid gives a very soft pedal, and won't be helped by 'hotter' pads). Perhaps have a set of EBC type pads to use when you're nailing it on track, swapping back to the standard stuff when you're on the road?
Lowering should increase the braking force at the rear if the bias valve is working as it should - as it appears to have more weight over the back. Could cause rear-wheel lockup, esp. in the wet.
Finally, is the brake servo working at all? To test, apply the brakes several (3-5 or a few more to be sure) times with the engine off. As you repeat the application, the pedal should get harder. Push the pedal down, apply a constant force, and start the engine. The pedal should sink towards the floor slightly as the servo amplifies the pedal input and pushes more fluid into the circuit.
If the pedal doesn't get harder initially then either there was no stored vacuum or the servo doesn't work. If the pedal doesn't sink when you start the engine, then the servo is dead. A dead servo will not stop the brakes working, but will make the pedal a lot harder - especially on a modern car with discs all round.
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RobinJI
Posted a lot
"Driven by the irony that only being shackled to the road could ever I be free"
Posts: 2,995
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Jun 16, 2012 17:29:52 GMT
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Lots of good advice and clever things....... Lowering should increase the braking force at the rear if the bias valve is working as it should - as it appears to have more weight over the back. Could cause rear-wheel lockup, esp. in the wet. ...... Lots of good advice and clever things. Nit picking I know, but it's actually less likely to cause rear end lockup in the wet, as the lower grip levels result in less forward weight transfer, so although there's less grip out back, proportionally, there's even less grip up front, so the fronts will lock first. But yeah, other than that, what James said.  |
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Jun 16, 2012 17:40:05 GMT
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Nit picking I know, but it's actually less likely to cause rear end lockup in the wet, as the lower grip levels result in less forward weight transfer, so although there's less grip out back, proportionally, there's even less grip up front, so the fronts will lock first. But yeah, other than that, what James said. Yeah, you're right, and I'm hungover. Regardless, you don't want your rear brakes locking up - it can get quite scary quite quickly. |
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ChasR
RR Helper
motivation
Posts: 10,309
Club RR Member Number: 170
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Jun 16, 2012 19:40:30 GMT
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Is your servo working? I would check that out as per jrevillug's instructions  . Agreed with the others, I'd ditch the pads first for some decent road rated ones (as mentioned, stock Toyota ones should be up to the job). I had no end of problems from EBC pads on one of my previous cars giving poor braking (lack of bite and feel). I changed them for some Ferrodo pads and the braking improved massively right from the outset, even before they were properly bedded in. The difference was immense. As also mentioned, try re-bleeding the system again going through the procedure recommended by Toyota. This and what Jrevillug said . On two cars I have had EBC pads on (a daily similar to what I have now with their stock Reg90 pads and driving a mate's Clio with Greenstuff pads) I can safely say I would run a mile with EBC stuff! The Mondeo's system (with a lighter 2.0 engine under the bonnet) was useless in braking full stop (Even the ABS would not kick in with me hoping I wouldn't rear end anyone. Cheapo Halfords pads gave a night and day improvement believe it not!) and in the case of the Clio they have curse word bite from cold, and were OK once warm (the same car on Mintex M1144s was a revelation). Some people have said EBCs have been fine on their cars but I certainly would not use them again on such a critical component of a car. Sorry if I am quite negative of EBC stuff but bar the pushbike stuff I really was not impressed with their car offerings. Out of the fast road pads I have tried the M1144s are probably the best road suited pads, with superb bite from cold and generally not fading out unless you push the car VERY hard on a track day (but I guess that's why M1155s are around  . It's one reason why I have '44s on the 205 (I do watch the rear view mirror a little more now if I am honest!). Ferodo DS2500s are near enough as good as the M1144s IME and I am told the Pagid Blues are pretty much like the M1144s (cheap however they are not!). Saying that, some good genuine pads or OE pads (from the likes of Bendix, Delphi etc.) should be fine. On the daily anyway the genuine Ford pads came with more meat (to the point I could just about put the caliper on when I put fresh discs on the car, more surface area (to cover the entire disc) in addition to lasting longer in comparison to what most motor factors sold. Cheap they were not, but doing an insane amount of miles over the year in addition to them being cheaper than most fast road pads made them a viable alternative (the joy of changing pads once every month (or 2) soon wears off!). I would have said to change your brake fluid (I am assuming that your fluid has been recently changed to some fresh fluid). That's been my experience of the various brakes anyway:). |
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Last Edit: Jun 16, 2012 19:42:19 GMT by ChasR
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zircon
Part of things
Posts: 327
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Jun 18, 2012 11:47:56 GMT
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Thanks all - I will have another poke about and test various things.
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Jun 18, 2012 22:23:05 GMT
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EBC redstuff's and a 1' bore master cylinder from the Tacoma. My brakes are curse word hot. Either that or four pot calipers of a 200sx and Gaz's nifty little brackets. That setup rips your face off.
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'95 Toyota MR2 Turbo
'72 Toyota Celica TA22
'74 Mercedes 350 SL
'68 Mercedes W108 280SE
'03 Renault Clio 172
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zircon
Part of things
Posts: 327
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^ 4-pots won't fit under my 16's mate.
Definitely going to change the pads though.....
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Jun 20, 2012 12:40:44 GMT
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if the pedal is hard even with the engine running and there is a marked lack of pedal travel/brake force then you have a servo assitance issue...its the only thing that will cause the pedal to go rock hard like that in a road car set-up
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if at first you don't succeed...use a gas axe!
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Jun 20, 2012 19:16:00 GMT
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Echo above comment, hard pedal and lack of confidence definately sounds like poor servo assistance. To test this I suggest pumping the pedal with the engine running, then switching the engine off and pump the pedal a few times more, after about 5 or 6 pumps it should go harder. If not then you don't have any servo assistance.
hth
Jon
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. It's one reason why I have '44s on the 205 (I do watch the rear view mirror a little more now if I am honest!). Ferodo DS2500s are near enough as good as the M1144s IME and I am told the Pagid Blues are pretty much like the M1144s (cheap however they are not!).
