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bigger injectors on a bpu motor?


Jamesy
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Larger injectors just gives a bit more headroom. Pretty sure that at 400hp the 440's are pretty much maxed. Also read that the transition between tubby's causes a bit of trouble but i don't know why.

 

Homer managed 430, the figures are really a guess though. You get different figures from different dyno's. The only figure that can be taken as gospel :sly: is the WHP.

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Hi Jamesy, I was always led to beleeve that if you are running full bpu you are better off with UK TT 550 injectors and a UK fuel pump, or equivelant, something to do with the possibillity of running too lean at top end power which can be dangerous.

 

Bob.

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so are you saying a bpu car running over 400bhp SHOULD have bigger injectors for better running and maybe adding to the bhp?

if so, what size ? 550, 780's 850's etc?

 

Larger injectors just gives a bit more headroom. Pretty sure that at 400hp the 440's are pretty much maxed. Also read that the transition between tubby's causes a bit of trouble but i don't know why.

 

Homer managed 430, the figures are really a guess though. You get different figures from different dyno's. The only figure that can be taken as gospel :sly: is the WHP.

 

Thought i should copy and paste as you must have missed it ;) You asked exactly the same question so the same answer seemed appropriate :p

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Surely adding bigger injectors are only going to be of use if you have a programable ECU to control them?

 

Hi Jamesy, I was always led to beleeve that if you are running full bpu you are better off with UK TT 550 injectors and a UK fuel pump, or equivelant, something to do with the possibillity of running too lean at top end power which can be dangerous.

 

Bob.

 

 

any idea if 550 injectors will drop in ok without having the ecu remapped or tweak etc?

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Jamesy, you may want to get this moved to the tech section you may get some good hits from some of the top tech hitters.

 

Yes I think you would have to get resistor pack but I'm not sure about ecu, "Keron" is the man to ask about second hand bits.

 

Bob.

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You need an ecu, piggyback or otherwise, to get the right amount of fuel coming out of bigger injectors :)

 

The resistor pack solves a separate issue - the difference between low-impedance (e.g. stock 550s) and high-impedance (e.g. stock 440s) injectors - so that the ecu sees the same resistance whichever type you have. (That's the simple explanation ;) ).

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That's right, yeah. An emanage (preferably ultimate) would do it, but you're looking at a fair bit of money all told for not a lot of gain.

 

If you're wanting lower 1/4 mile times, you might do better investing in drag wheels and tyres... I don't know, just thinking out loud :)

 

If you want as many horses as possible, best start saving for that single conversion you've always dreamed of ;)

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Jamesy, I'll try and explain, though there is no hard fast rule. It's more complex than it might appear.

 

You *can* run a jspec car at 1.25 bar on 440cc injectors and acheive up to 360rwhp on a 6spd (done it). The injectors will be at 100% duty and the AFR's will be border line while the 2nd turbo is spooling up, it will drop to rich levels at peak,

 

It's impossible to change to a larger injector without an aftermarket ECU and map.

 

The biggest risk with running BPU at high boost level is not at high RPM, it's at mid range RPM when the stock ECU map stuggles to supply enough fuel. At high RPM and boost they will still run fairly rich.

 

You will not get any more bhp from changing to larger injectors in itself, the turbo's and even with a top end IC and stock intake are already beyond their efficency range. However a larger injector combined with an aftermarket ECU and map will help remove that nasty lean point and maximise the power delivery through the range.

 

My SRR record (which has stood for 5 years) was only beaten this year by a stock turbo'd car with an aftermarket ECU - mapped by Ryan.g :thumbs:

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thanx for taking the time to explain mate.

 

my bpu is currently running at around 1.2 to 1.24 bar.

 

at 1 bar and pre FMIC fitted it made 407fwhp so was thinking now the fmic is in and the boost has been upped i "should" be running about 430fwhp :search:

 

therefore i guess i am pretty much maxing out everything.

 

shame u cant just stick in the 550's but i will wait until an e-manage ultimate comes up and maybe go that route then..... (or just go single!!) :D

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thanx for taking the time to explain mate.

 

my bpu is currently running at around 1.2 to 1.24 bar.

 

at 1 bar and pre FMIC fitted it made 407fwhp so was thinking now the fmic is in and the boost has been upped i "should" be running about 430fwhp :search:

 

therefore i guess i am pretty much maxing out everything.

 

shame u cant just stick in the 550's but i will wait until an e-manage ultimate comes up and maybe go that route then..... (or just go single!!) :D

 

What rolling road were you on though? It varies immensely as people seem to calculate the FWHP differently. RWHP gives you a much more accurate reading of the power of your car. If Homer made 360RWHP then thats what you should be aiming for, if you want to beat the 430 record then you would really need to go to SRR as anywhere else would do the calculation differently giving you more or less than you have in comparison.

 

At Dyno days you can see the difference between different dyno's from people who have had their car at different places. Sometimes they make more, sometimes they make less. The operator can pretty much give you any figure you want though. Some like happy customers, some like to be honest. Its always funny that we believe the highest figure is the most accurate though ;)

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