911

I'm a bit lost here so need some help.

I have an STi V3, runs 1.25 bar, setup at Power Eng and delivers 314bhp. The car is seriously thrashed hillclimbing, very flat-out.
PE told me the injectors were at the extreme of their duty cycle. If I fitted bigger injectors could I firstly sleep better knowing it won't go bang, and more importantly, can I boost it more, say 1.35 and gain more bhp BUT not hit fuel cut-off?
I have a Blitz boost control fitted. apart from a 2 3/4 stainless decat system, the engine is bog standard.

What size injectors does it have anyway, 430cc?

Graham.

madou

Graham

It has 440 cc injectors

PEng should tell you exactly what injector duty cycle your car is running. 85% is a reasonable maximum

Larger injectors, like 550 cc allow the same amount of fuel at lower IDC, but you need to re-map, running the same pulse width on larger injectors would obviously cause over fuelling

You don't say if you have any Engine management apart from the Blitz Boost controller and Standard ECU ( with PEng piggyback ? )

Fuel cut off is a function of the Stanard ECU, that's why when people play with bleed valves they get the rocketship hitting a brick wall feeling

Time to get one of the good engine management guys like Bob, Mark, or Pat on the car. This will be cheaper that a blow up


[Edited by madou - 5/5/2003 9:09:38 PM]

911

Thanks for coming back so quickly, all makes good sense. The car has standard ECU and I was told by Power Enginnering that the injectors are on maximum duty. No idea what percentage that is.

Regards

Graham

madou

Graham

Rule of thumb result from my MY98 UK with BRD Link, Full Decat, and Sytec http://www.fuelsystem.co.uk/injection.htm uprated fuel pump, which matches almost exactly what it makes on a rolling road

4 * 380 ( cc ) * 0.86 ( IDC ) / 5.5 ( bhp per cc ) = 237.67 BHP

If you are at extreme 95% IDC

4 * 440 * 0.95 / 5.5 = 304 BHP

Divisor is the contentious number ...

911

Looks good, but where did you get the 5.5 bhp/cc from?
Also, Power Eng's rolling road gave 314 bhp @ 1.2 bar on Optimax. I bet they can coax the rollers to give a 'good' result, but they can't be very far out?
The stock STi V3 is rated @ 275 ish bhp on 100 octane, but I don't know what boost level is stock (1 bar?)

Thanks for your input though, I need to get more from the engine but reluctant to go to GEMS or even MOTEC and all that goes with it. A friend has GEMS on a stock RA V3 and it doesn't seem much quicker than my car.

Regards, Graham.

madou

Graham

Range of 5 - 5.5 cc/bhp previously quoted on this forum, I raise it again because it does seem to be a close approximation in our two cases. Bit of a shame for me, as "le tout monde" has 240 bhp+ from just a de-cat and panel filter change, must take all the kit back and complain

You can coax rollers to give results, depends if you are buying or selling. Power Ponies (tm) are large and sturdy animals

I was reluctant to go for a standalone ECU for a long time, but most of it was due to the old wives tales that clutter up the board. What is your worry in "all that goes with it" ? I run the car all the way from cold start down to Waitrose to the Furka Pass and haven't had any problems

If you are running competive times to an STi V3 RA with GEMS, it's a credit to your current set-up and driving - any chance of telemetry to figure out the balance between these ? Throttle and Brake overlays are usually informative / depressing

You must see a lot of good engineering when you are competing in hill climb, especially the single seaters, why not ask some of those guys about engine management ?

911

My friends RA is a great car. I've driven it hard on a sprint track and it's a realy good package. He has a cold air box, Gems, anti-lag and a BPM system fully decat. He also is irritated at the mapping as he can't find anyone 'aggressive' enough with the set-up, and this is what I meant about' all that goes with it'.
He has DMS Gold struts and a good set-up with 7.5 x 17 wheels from BBS etc.
My route to 'fame' is a full house Whiteline set-up with no rubber bushes anywhere along with a radical set-up again based on Whiteline advice, especially the front Caster angle.The engine is stock STi V3 except the exhaust and a Halfords (!) panel filter.
The engine is realy nice, but I'm up against cars with 50/80 bhp more, it is a big gap to bridge by suspension/driving alone, and I'm too old to be a hero.

I also drive the car hard to scare myself and as if I hate it, a common Hill climb approach!

Have no access to laptop downlods, but this is VERY commonplace on the hills, there are some mega cars racing, the quickest has 1300bhp/ton.....................!
Regards, Graham.

hypoluxa

Graham,

Regards mapping, there is only so far you can go with a stock set up. STi's tend to have quite aggressive maps to start with.

To really benifit from a GEMS or Motec, especially on lesser quality fuel, you need a larger turbo/intercooler and an uprated fuel pump/adjustable regulator. The turbo will allow you to flow more air at lower temps at similar boost, the regulator can be set up as to deliver more fuel pressure (which will basically 'enlarge' the 440s). A front mount intercooler may have a negitive impact though regarding hillclimbs (and your wallet), probably wise to monitor your inlet temps over a few runs with the OEM intercooler. A standard set up on a GEMS ecu would be to pull 2 degrees ignition timing out for every 10 degree inlet temp rise (starting at 50c IIRC).

Turbo, pump, reg, GEMS and mapping should cost you circa 2.5k. Should give you up to 350hp at PE.

Not exactly what you asked, but food for thought anyhow

I think I may have spoken to your RA friend before, are they gold split rim BBS wheels?

CarMan

Hey you guys, stop talking about me like I ain't here!

I reckon some datalogging of inlet temps + throttle/brake and wheels speeds etc would be really useful.

When I was young (a couple of years ago!) I was mountain biking with an F1 IT mate who thought money spent on data stuff would be minimal compared to "more power"?

Rgds (V3 RA + BBS etc!!)

911

Jesus Carman I thought you were busy with bricks and mortar!
My original thought was if I went to bigger injectors with a Motec Link Gems ECU would I find a real BHP benefit? there is always the BHP/£ debate. 2K on all of this for a weedy 30 bhp gain is poor value. Bet I might get more on track performance by tuning the Driver first for 500£!!
Like the fuel pump idea though.
Regards to all, Graham.