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mods for jspec supra


eyefi
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i am very keen to mod my 93 jspec mk4, i've been running stock for 5 months now (except for hks priest zaust), i think thats long enough.

 

i am new to tuning & modifing. just jumping in and changing this that & the other with no consideration of its full effects is not for me. the last thing i modified was my raleigh grifter! so any answers or alternatives would be most helpful.

 

my initial idea was to get a set of chris wilson downpipes, waterspray, egt + boost + oil gauges, digi boost control, fuel cut defence (petes) & RL traction control. all this seemed fine until i read more & more & more. the more ive read the more confused ive become. (ive read nearly all the tech brd)

 

my points of confusion / concern are:

 

1/ are there 2 cats only in supra and are they in separate sections of the downpipe?

 

1a/ no cats have been removed by my existing hks system ?

 

2/ removal of both cats on jspec creates wild uncontrollable boost, but this can be controlled with a CW downpipe that is 2.5". this gives a steady reliable boost of 17/18 psi which can not be returned to stock by use of digi boost control. true or false ?

 

3/ ash reckons running more than 14 psi of boost is asking for trouble (i dont want  trouble)

 

4/ does waterspray cooling cancel the effect of xtra heat generated by higher boost, or is it just a safety (stop preignition) thing ?

 

5/ boost controllers on stock turbos is a waste of time ?

 

6/ egt, oil temp & boost gauge are all i need to keep a close eye on my engine ?

 

7/ there is no xtra fueling beyond 14psi from ECU?

 

8/ cars pre 94 dont need cats for MOT emmisions?

 

9/ does anyone else think the electronc HKS gauges are very expensive?

 

10/ can u run higher boost with the standard downpipe and digi boost control, if so what psi?

 

11/ anyone else running similar mods what MPG do u get ?

 

12/ when does the jspec fueling system (injectors or pump) max out ?

 

13/ what sort of bhp and torque figures would u expect from these mods ?

 

14/ would a 2.5" downpipe be too restrictive for bigger turbos ?

 

i think i best stop there..

 

 

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1. Yes

1a. No

 

2. Some people claim it can be lowered again by the use of a boost controller but this seems a little pointless to me. Once you've had 18psi anything less feels a little dull.

 

3. Quite possibly. Any increase in power will stress your engine more and shoreten the life of some components. It depends how much you are prepared to upgrade and how much risk you are willing to take.

 

4. It will lower the temp and I personally see it as a safety thing. I prefer an FMIC really with WI as well if you want.

 

5. Not really. If you keep the cats it is a good way of raising the boost.

 

6. These are all very useful gauges to have.

 

7. Thats right, the FCD clamps the signal at fuel cut level so the ECU is effectively 'blind' to boost beyond this level.

 

8. Mine needed one refitted to pass emissions and its a 1993. It's a grey area, you may get away with it and you may not.

 

9. Yes, but they look nice. I'm sure Ringmaster can do you a deal.

 

10. Yes, whatever you want really but no real point in going beyond 18psi on stock turbos.

 

11. MPG will be probably high teens depending on your right foot.

 

12. I think around 440BHP theoretically but Ash will probably be able to give you a better estimate and reason why.

 

13. Maybe 350 to 400 crank BHP

 

14. Apparently not according to CW. I believe the bottleneck is created by the manifold.

 

I think the above is fairly accurate although I am by no means an authority on these matters.

 

FWIW I run a TT aerotop with CW downpipes, a HKS Hiper and a HKS Induction kit, no TC until my Racelogic goes in, a HKS S type FMIC, 18"s and Eibach Springs.

 

18psi and it runs sweet on Esso SUL with Millers Octane Booster and an oil change with Valvoline every 4000 miles.

 

Cheers,

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If you're going to fit a FCD you really should fit one of Pete Betts. It doesn't removed the fuel cut, it simply moves it higher. It retains the safety limit at 18 psi.

 

If you fit Pete's FCD and a good quality bleed valve, I don't think you need to worry about de-cat pipe diameter. Chris defines his pipes at 2.5" to prevent boost creep. I'm running 3" APEXi pipes on the stock exhaust and that works fine. When I go to the Super Drager or a Mongoose, then I'll fit a bleed valve at the same time.

 

Talking to Toyota Service Manager today and he told me Toyota are buggers for building an engine and then suffocating it for reliability. He thinks the Supra TT engine is 450+ BHP in it's native state and Toyota have done their usual trick and limited everything. He told me the TT engine will rev through the ceiling (assuming you do *everything* else needed to take advantage of the extra RPM).

Shan't be doing that, thank you very much, but it certainly was good to get his opinion. He *did* warn about unrestricted boost and his experience with a *number* of people melting their pistons.

 

 

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The only "full" effect you need to consider is the amount of money you wish to spend. If you want horsepower on the cheap read the adverts, believe them, then talk to the (so called) leading tuners.

 

Yours,

 

J

 

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Quote: from Paul Booth on 3:59 pm on Oct. 12, 2001[br]

.

 

If you fit Pete's FCD and a good quality bleed valve, I don't think you need to worry about de-cat pipe diameter. Chris defines his pipes at 2.5" to prevent boost creep. I'm running 3" APEXi pipes on the stock exhaust and that works fine. When I go to the Super Drager or a Mongoose, then I'll fit a bleed valve at the same time.

 

Paul , with both cats out you may find the bleed valve redundant. It can only provide more boost , it cannot lower boost levels.

I'm using one , but still have the 1st cat in place. I believe you will have boost thro the roof with 3" d/p's and a performance 'zaust.

 

HTH

 

 

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Quote: from matt on 12:55 pm on Oct. 13, 2001[br]
Quote: from Paul Booth on 3:59 pm on Oct. 12, 2001[br]

.

 

If you fit Pete's FCD and a good quality bleed valve, I don't think you need to worry about de-cat pipe diameter. Chris defines his pipes at 2.5" to prevent boost creep. I'm running 3" APEXi pipes on the stock exhaust and that works fine. When I go to the Super Drager or a Mongoose, then I'll fit a bleed valve at the same time.

 

Paul , with both cats out you may find the bleed valve redundant. It can only provide more boost , it cannot lower boost levels.

I'm using one , but still have the 1st cat in place. I believe you will have boost thro the roof with 3" d/p's and a performance 'zaust.

 

HTH

 

 

Sugestions? Boost controller?

 

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It's been mentioned before, but you really ought to have bigger brakes on your list (near the top) as well. Now I've fitted UK Brakes, I can now consider upping the power. Going fast is great, (road/traffic/weather conditions permitting) but it's even better if you get a second chance to go fast. Better brakes may give you that second chance.

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Quote: from Simon on 9:07 pm on Oct. 13, 2001[br]It's been mentioned before, but you really ought to have bigger brakes on your list (near the top) as well. Now I've fitted UK Brakes, I can now consider upping the power. Going fast is great, (road/traffic/weather conditions permitting) but it's even better if you get a second chance to go fast. Better brakes may give you that second chance.

 

If your posting is for me, you don't read all the threads, do you Simon?

 

I've had my BIG brakes sitting on my garage floor in a BIG crate waiting for some custom made flexible hoses (to my spec.) and the right wheels, for about 3 months.

The de-cat pipes were fitted out of synch because they came along at the right price and the right time. They're fitted with the stock exhaust to limit the number of issues I have to deal with at the same time.

 

 

 

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No it's not for you Paul, I know you've had the brakes waiting, also you and Ash were the only other people who have said 'wsort your stopping power out first' or words to that effect.

The post was intended for eyefi who had all the power mods listed but no brake mods. (unless I missed that)

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Quote: from Simon on 9:19 pm on Oct. 13, 2001[br]No it's not for you Paul, I know you've had the brakes waiting, also you and Ash were the only other people who have said 'wsort your stopping power out first' or words to that effect.

The post was intended for eyefi who had all the power mods listed but no brake mods. (unless I missed that)

 

Well spotted that man.

 

I noticed that too but it makes me feel like an old fart (being one and feeling one are two different things) making that point every time someone asks about improvements.

 

We should have a page with all the options on and the BIG brakes options should be at the top of the list.

 

See, now you've got me on that blasted soapbox again. NURSE!!, my medication if you please.........

 

 

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Ahhh, but hang on a minute . . . . did anyone read Chris Wilsons *excellent* post on the supra mailing list on the subject of braking, big brakes, and all the issues relating to it?

 

I think I can summarise it thus:

If your stock brakes offer enough retardation to lock the front wheels (or activate the ABS) then fitting bigger brakes will offer no increase in ultimate stopping power.

Fitting fast-road or race spec pads (especially the really good ones like portefields) along with good brake fluid should offer enough fade resistance, even on j-spec brakes, for almost any road use.

Fitting UK brakes with fast road pads will be more than adequate for almost any track use.

If you have fast road pads fitted and you're on track every weekend and you're munching through discs and pads at some exorbitant rate then you might need BIG brakes

 

Huge discs will offer an increase in retardation at a given low pedal pressure, so it might feel like they're working better, but ultimate stopping distances will remain the same - ie a function of the effectiveness of the driver, or the ABS, and the front end grip of the car.

 

I'm by no stretch of the imagination an expert, just passing on what I can remember, but it's something I read which you may like to check out because I was struck by how much sense it made.  Apologies if I've misquoted or got it wrong or whatever . ...

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I've found the email from Chris Wilson that Adam's referring to.   It is a good post.   here's the text written by Chris :

 

****

> Has anyone done any comparisons between the braking ability of UK spec discs and pads fitted to a MkIV TT Import and after market brakes like AP, Brembo etc.

 

The stock brakes will stop the car as fast as AP or Brembo, don't think

big brake kits will decrease stopping distances, they won't. If a braking

system is powerful enough to be able to lock the wheels, and has the

correct front to rear balance and can be modulated then bigger brakes

WON'T make the car stop faster. What they will do is allow the car to

stop ultra hard time after time with short recovery periods needed

between stops.

 

Ask yourself these questions, reply honestly, and see if you NEED big

brakes.

 

Have the brakes ever suffered pad fade? That's when the brake pedal

stays high and hard, but the brake pads get so hot the coefficient of

friction drops to nearly zero and the car doesn't stop. If you get this

it's probably on a track. Uprated pads and fluid will fix this for about

90% of track day usage.

 

Have you suffered fluid fade? This is where the fluid boils and the

pedal literally flops to the floor, zero brakes. Quite frightening! This

can be fixed with decent performance brake fluid in most instances.

 

Do you repeatedly use the car  ultra hard on race tracks, have tried harder

pads and race fluid, yet still find the stock brakes suffer fade, pad

wear is ludicrous, and the heat generated is melting things and killing

wheel bearings? Then you NEED bigger brakes.

 

Otherwise a big brake kit will look nice, possibly convince you that the

car stops in a shorter distance, but most of the time you will not get

much advantage from it.

 

I REALLY believe that even J-Spec brakes will work very adequately for

most users, even on track. UK brakes will work fine on track for all but

budding serious race drivers, and even then you'll need road legal race

tyres to get them to wilt.

 

AP brake kits for the Supra are superior to Brembo. Bigger disc

diameter, bigger pad area. Can be a PITA to get under the wheel, make

sure you CAN get either Brembo or AP under the rims before you buy none

stock wheels. Safest bet with AP is use the wheels the kit was designed

for, Gewalt Mackins.

 

Here are pics of AP and Brembo kits side by side. I can supply either

kit, or even Wilwood caliper kits for the MKIV. The Wilwoods work fine

and are a worthwhile amount cheaper than AP or Brembo.

 

http://www.formula3.freeserve.co.uk/ap-brembo.jpg

 

AP kit is on the left. Brembo kit comes with drilled discs which will

crack given serious hard usage. If you aren't going to give them serious

hard usage why buy them :-)

 

--

Best regards,

Chris Wilson

****

 

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Yes, it's all a bit elementary though isn't it.

 

What it doesn't cover, at least I dind't see it, skimming through, is the extra forces placed on the brakes on fitting larger diameter wheels and/or wider tyres. I won't make this a mammoth post by going into the physics and anyway, I don't happen to like standing up on my pedal every time I need to stop in a hurry. I'm at an age where I want shopping trolleys to have PPS and vacuum assisted brakes.

 

The one point I picked up worth noting was that the recovery time goes down.

 

Either way, I understand the issues, what my purpose is and what the overall effect will be.

 

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Quote: from Paul Booth on 2:51 pm on Oct. 14, 2001[br]

Either way, I understand the issues, what my purpose is and what the overall effect will be.

 

That's cool.  It's just from the general tone of the posts - "If I have fifty extra bhp then when I hit the brakes nothing will happen and I'll die" - I got the feeling people were expecting miracles.  Big brakes won't make any difference in an emergency stop situation, they just stop your pedal going all mushy at the end of a long fast run down a windy road!  Which is a Good Thing, obviously, but my point was that tuning your car without improving the brakes isn't suicidal . . . . isn't Leon running stock J-spec brakes?  IMHO, etc, etc .. . :)

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My experience is that I should have done my brakes a long time ago. I have been trying to get a set of UK fronts ever since I put UK wheels on, but they are pretty rare second hand. I have just bought and fitted a new set of UK fronts, and even whilst running them in they feel better than the J-spec.

 

I also suffered ridiculous pad wear at the last track day on the J-Spec. I put on a set of CW intermediates, bedded them in properly, and then went through the whole set at Bentwaters! The braking was good, but it still faded, and a set of pads lasting for an afternoon was not quite what I expected!

 

IHMO the J-Spec could probably be made good with a decent overhaul and pads, but the UK spec new is less than a grand for the complete setup. I spent that on a FMIC to protect the engine, so you should see it as a bargain to spend a similar amount to protect your soft squishy body!

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i'm a bit concerned about pad wear on track days too, so can anyone else give us the benefit of their experience with regards to pad wear on track days ?    I'm running Porterfield R4S pads (which are the equivalent of the CW Intermediates i believe).    I did a 17minute track session at Silverstone and haven't checked the pads since, so i've no idea how much they've worn.      They're not cheap at all (like the CW ones) so i'd hope they wouldn't get trashed in 1 day.

 

I've got UK brakes so they should wear the pads a bit less on the basis that the pads have a greater surface area than the J-spec pads and therefore, for a given retardation, the pads should wear less than the same compound used on a J-spec brake set-up.

 

JB ?   Phil Duley ? Gavin ? Paul Whiffin ?    can you comment here ?

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Quote: from Adam Wootten on 8:26 pm on Oct. 14, 2001[br]
Quote: from Paul Booth on 2:51 pm on Oct. 14, 2001[br]

Either way, I understand the issues, what my purpose is and what the overall effect will be.

. . . . isn't Leon running stock J-spec brakes?  IMHO, etc, etc .. . :)

 

No...he's running UK spec brakes and Porterfield Road pads.

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I've got J spec calipers with CW Race pads and they are excellent.

 

The wear is greater but I've done 2 track days and a lot of road miles and they still have some meat left, the standard pads don't seem to wear at all but then they don't work either.

 

I read the previous posts with interest but would say that in the real world the CW race pads increase the braking ability of the car many, many times.

 

The stock pads are dangerous in my opinion and a liability from high (track day) type speeds.

 

Cheers,

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There are three primary facets to the braking argument IMO.

 

The first has been amply covered in the above posts, namely, the respective ability of brake setups A & B to bring the car down from a high speed X to a low speed Y... in Z amount of time.

 

Such a comparison may well conclude that both braking setups are of equal ability. However, this comparison fails to take account of the fact that the act of braking is not a one-off event.

 

For a true comparison to be made, the experiment would have to include a representitive cycle of braking actions over a determined duration.    

 

The third facet is a comparison of component service-life and the cost of operation over time.  

 

There are other relatively minor issues which I would say could be considered important to some owners. Such as brake squeal, component service-life, better looks, and so forth.  

 

Yours,

J

 

 

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Personally, I switched because I found that I was suffering fade on the road - OK so I do a lot of hard accelerating and braking which isn't the best way to drive - For my driving style I have fount the new setup even with standard pads to be superior.

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I also suffered ridiculous pad wear at the last track day on the J-Spec. I put on a set of CW intermediates, bedded them in properly, and then went through the whole set at Bentwaters! The braking was good, but it still faded, and a set of pads lasting for an afternoon was not quite what I expected!

 

I ran Porterfield R4-S  and DOT5.1 on the Supra at Bentwaters with no fade and little pad wear, braking from about 120-125MPH on the back striaght and 100-110MPH before the pit. The R4-S is a really good pad, can't compare them to the CW ints. as I never used them. I have the R4-S them on the Teg R, first thing I fitted.

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