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fuel system, help me decide??


eyefi

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im ready to order my fuel system, but cant quite make up my mind. i have 2 basic options :-

 

1/ increase fuel pressure, new pump and rising rate reg. overdrive those 440's. its done on quite alot of cars, cheaper, easier to do, but not quite right.

 

2/ as above but with some big ass side feed injectors. the injectors will b a bit big for my immediate needs, its about £600 more, still not too difficult to do, more correct, a bit more mapping work, future proof.

 

i have custom exhaust work from the turbo exit removing all the blockages and am aiming for around 500hp.

 

i know it makes sense to go for the bigger injectors but if its sound to do it without then why bother? i dont really have the luxury of getting it mapped on the stock injectors only to find problems then have to map it again on bigger injectors. money is always a concern :)

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Originally posted by eyefi

im ready to order my fuel system, but cant quite make up my mind. i have 2 basic options :-

 

1/ increase fuel pressure, new pump and rising rate reg. overdrive those 440's. its done on quite alot of cars, cheaper, easier to do, but not quite right.

 

That is what I've just had done to mine, bought new ingectors and stayed with the 440's but increased pressure. OK to about 18PSI on stage 3 hybrids apparently.

 

I think the general rule for the Supra is 1cc per HP, so for 500 BHP the 440's would not cope.

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Guest Terry S

Do the modified exhaust work as I may be selling my DE fuel rail & sidefeed 850's in a while;)

 

On the fuel pump I would happily raise the pressure but you must make sure of the condition of your pump & a pressure gauge would be nice.

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yep, ive decided on a new pump and reg, so it should b ok. like u say a small drop in pressure (at the very high pressure the 440's would have to b run at) could b disasterous. it would b really difficult to keep an eye on that, cos u cant setup a warning light for x pressure at y revs. ive got a wideband to go in the car, so that could b useful for a backup warning.

 

hmm, it could end up just being a worry with the small injectors and gazing at gauges rather than the road when on boost.

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Guest Terry S
Originally posted by eyefi

im planning on running more than that :) my sensor can cope with about 32psi of boost

 

My sensor goes to 45 psi but I sure as hell won't be running it!!

 

Be careful Eyefi. You will either need to back your timing right off or run turbomax fuel.

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u dont need lines just yet, u dont really need bigger injectors yet. it just depends what yr happy with.

 

the problem ive got is the spending has to stop :( so after this, thats it for me (jesus, that really pained me to say that). so i need to get it right this time. all my notions for cosmetic mods have had to go out the window.

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Originally posted by Terry S

My sensor goes to 45 psi but I sure as hell won't be running it!!

 

is that absolute tho, mine'll do that :)

 

i knew as soon as pressed post that someone would have to say that :). nah i wont (cant) b running 30 odd psi of boost, but i will b running more than 18.

 

Originally posted by Terry S

back your timing right off or run turbomax fuel.

 

i have fuel plans ;)

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Guest Terry S

There is a practical limit on both lines & injectors. If you are doing it properly the injectors should change, the FPD should be removed. There are limits to a -6 line also. Two would be nicer. You should hear the noise form my - 6 stock return line with two -6 lines feeding the rail. I may need to to change the return to -10 I think.

 

It all depends on goals

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Originally posted by Terry S

There is a practical limit on both lines & injectors. If you are doing it properly the injectors should change, the FPD should be removed. There are limits to a -6 line also. Two would be nicer. You should hear the noise form my - 6 stock return line with two -6 lines feeding the rail. I may need to to change the return to -10 I think.

 

It all depends on goals

 

the stock lines should b fine for my needs tho, shouldnt they? i hope so.

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so is there an idiots guide to what one could do from scratch to jap fuel system

 

eyefi you have changed a few things and sensors

also the map sensor i think its called. does that allow you to run more boost. i would like to do some but dont know where to start. and dont say the begining

 

what would you need to run say 1.4 bar along with cooling mods. and electronic boxes or ecu

i know this is where it starts to get expensive.

 

thanks

 

theres some monkey coffee in it for you :eek:

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Originally posted by Terry S

Depends what you are trying to achieve, & how safely.

 

leons pump & reg, 22-24psi, big inj (like we spoke about), stock rail, hybrids. something between 400-500hp. doesnt have to b perfect, but not a constant concern everytime u get on it. surley those lines will b fine.

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Guest Terry S

stock lines will be fine at 500 bhp

 

Monkey, it's all about octane & compression ratio's. 19 psi seems to be the limit for our 8:5 :1 engine on Optimax with stock ecu. Larger injectors won't change that.

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Originally posted by eyefi

the problem ive got is the spending has to stop :( so after this, thats it for me (jesus, that really pained me to say that). so i need to get it right this time. all my notions for cosmetic mods have had to go out the window.

 

Stop spending money on your car and get that downstairs toilet sorted! :p

 

...oh and the windows, and....

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Guest Terry S
Originally posted by Thorin

but then you could fit a thicker head gasket and run higher boost on optimax?

 

True but then you'd lose low down response. It seems an expensive way to run a *bit* more boost.

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On pump fuel, where is the point where the ignition retard at high boost becomes so great that you don't actually make any more power as the boost goes up?

 

Terry, do you run one line from each pump all the way to the rail or do the two join into one line, run under the car, then go back into two? I was planning on doing it the first way, but I've heard that most people do the second, can't see why though.

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Guest Terry S
Originally posted by Adam W

Terry, do you run one line from each pump all the way to the rail or do the two join into one line, run under the car, then go back into two? I was planning on doing it the first way, but I've heard that most people do the second, can't see why though.

 

1 line from each pump right the way to either end of the fuel rail. Each line has a filter. You can buy weld on bosses if you need a -6 connection at the other end of the rail.

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