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Injectors for GSXR TBs
chriscook - 25/11/06 at 11:42 AM

So I've got my GSXR 750/1000 throttle bodies complete with their reputedly 270cc/min injectors. The megasquirt calculators suggest that these should just about be ok for 180bhp which is what I have from my carbs now. However, I'm hoping to release a little more power and don't want to overdo the duty cycle at full power. So I have two options:

1) Use a higher fuel pressure of 3.5-4bar instead of the standard 3bar and use the GSXR bodies.

2) Use some car injectors of a higher flow rate ~300cc/min

But can std car injectors be used in the GSXR bodies?

The other decision to make is between the standard Vauxhall injector locations and the GSXR locations.

Thanks,
Chris

stevebubs - 25/11/06 at 11:46 AM

yes, but you'll run into 2 issues:


1) Fuel rail becomes a really tight fit so you'll need to find some suitable O-Rings or replace the rail. As I respaced mine to DCOE spacing, I replaced mine with an off-the-shelf Jenvey item

2) Car injectors are a little longer so you'll need to space the rail away from the bodies a bit.

Reference pics here

S

[Edited on 25/11/06 by stevebubs]

chriscook - 25/11/06 at 12:15 PM

Steve,

Can you remember which fuel rail it was?

I think I'll probably buy some injectors off ebay anyway, and see how they fit if the price isn't too high

Ta,
Chris

stevebubs - 25/11/06 at 05:11 PM

TBR 22 - http://www.jenvey.co.uk/Accss1.htm#FuelRails...

Note the pic on the right...

stevebubs - 25/11/06 at 05:13 PM

You should be able to pickup a set of Cossie dark blues for about £30 if you hunt around...should be fine for a normal/mildly tuned Vx

stevebubs - 25/11/06 at 05:14 PM

If you want injectors the same size as the bike ones, then IIRC they're known as Pico Injectors. Not that cheap or common though.

Standard car injectors fit the std rail fine without the top O-Rings. Thinner O-Rings would solve the problem.

S

Steve Lovelock - 26/11/06 at 11:06 AM

I am at this stage as well as was planning on using the standard Vx injectors, fuel rail and pressure regulator but I have no idea if it is a good option?

stevebubs - 26/11/06 at 01:03 PM

quote:
Originally posted by Steve Lovelock
I am at this stage as well as was planning on using the standard Vx injectors, fuel rail and pressure regulator but I have no idea if it is a good option?


If the facility is there, I'd use it. Swapping std Vx injectors for other car injectors, e.g. Cossie, is then a trivial exercise.

chriscook - 26/11/06 at 06:28 PM

Thanks for the info Steve. I don't have any of the std VX bits but my carb manifold does have bosses which could be machined for injectors and are pretty much in the same place as the OE locations.

Was being too tight last night to win the injectors I was looking at but did win a fuel pump and I've been building my MS2 this weekend too - just about to check the inputs with the Stimulator.

Chris

stevebubs - 27/11/06 at 07:35 PM

Cool..so if you decide to turbo it later, you already have positions to mount a second set of injectors.

chriscook - 27/11/06 at 09:32 PM

I like your thinking

Or for the NOS

NS Dev - 28/11/06 at 04:42 PM

Got a set of std vauxhall cream injectors going cheap if they are any use Chris? Good for 220hp

MikeRJ - 28/11/06 at 05:37 PM

quote:
Originally posted by NS Dev
Got a set of std vauxhall cream injectors going cheap if they are any use Chris? Good for 220hp


This is something I haven't been able to fathom out yet. The cream injectors (Bosch 0 280 150 744) are apparently only rated at 214cc/min at the default 2.5 bar, yet SBD retain them for their 208 kit.

If you look at the formula to estimate required flow rate for a given power (e.g. http://www.injector.com/injectorselection.php ) then these need to be run at around 95% duty cycle to achieve the stock 155bhp output. To get the recommended 80% max duty cycle would seem to require the pressure raised to around 3.5bar.

I can hardly believe Vauxhall would be fitting injectors with such marginal flow ratings (or would they?). I've asked about this on the MS forums before but never got any sensible answers.

Oh yeah, flow information is from the very useful flow data table at http://www.max-boost.co.uk/max-boost/resources/injectors-basic-info.xls

EDIT: Unless the B.S.F.C. of the XE is significantly better than the 'average' figure of 0.5 lbs/hour? I was always very impressed with the mileage my 16v Astra used to return.

[Edited on 28/11/06 by MikeRJ]

chriscook - 28/11/06 at 06:43 PM

I've wondered about this too it does seem odd. If they flow enough then the gsxr ones should be ok too - then I just need to sort out the fuel rail spacing. But having said that Neil Everett (nre) is running his zetec Mojo on the gsxr injectors and they are at about 85% max duty and estimates about 160bhp I think.

NS Dev - What injectors do you have on your 200hp XE?

MikeRJ - 28/11/06 at 10:10 PM

quote:
Originally posted by chriscook
But having said that Neil Everett (nre) is running his zetec Mojo on the gsxr injectors and they are at about 85% max duty and estimates about 160bhp I think.


Do you know what fuel pressure he is running?

It is a mystery, I have to wonder if 214cc/min is the correct flow rate for the cream vauxhall injector. Lots of different sources on the web state the same number, but they probably all got the information from the same place.

Interested to know as I have a set of GSXR TB's for my XE which I have respaced (if/when my locost project gets back on track!).

chriscook - 28/11/06 at 11:25 PM

3bar I think. Info somewhere on www.mymojo.co.uk but I need to get some sleep now.

nre - 29/11/06 at 08:02 AM

quote:
Originally posted by chriscook
... Neil Everett (nre) is running his zetec Mojo on the gsxr injectors and they are at about 85% max duty and estimates about 160bhp I think.

<Wakes up...>
Yes indeed, I'm running GSXR750 injectors on a 2.5bar bosch regulator on my 1.8zetec, and as Chris says I max out at about 85% duty cycle. No rolling road data, but it should be in the 160bhp region going on other peoples' experiences... It's not unusual to run up to 4bar fuel pressure, so maybe that's what SBD do to get the creams to flow enough?

nre - 29/11/06 at 08:17 AM

Oh, just to add, I used the attached little spreadsheet which is based on the usual assumptions floating around the web. It allows you to play around with fuel pressure/flow rate/max duty cycle. Bunging in the data for the mojo (270cc/min rated at 3bar, but running at 2.5bar at 85% duty) gives approx max power of 167bhp, so that sounds about right. Bunging in the Bosch injectors shows that running at 4bar and 95% duty cycle scrapes it to about 205bhp, so maybe SBD just cut it very fine...?

Neil

chriscook - 29/11/06 at 06:13 PM

Thanks Neil useful spreadsheet that for playing around with different numbers. I'm increasingly thinking that I might use the gsxr injectors - after all I already have them.

Neil didn't you get your suzuki rail modified to respace it? I've taken mine to bits and its trivial to extend the middle bits but you have flow in one end and out the other. Easy enough to machine the holes in but how do the ends stay in place?


Hope you don't mind me 'borrowing' your picture.

ta,
Chris

Also NS Dev, u2u sent

[Edited on 29/11/06 by chriscook]

nre - 30/11/06 at 08:14 AM

quote:
Originally posted by chriscook
Thanks Neil useful spreadsheet that for playing around with different numbers. I'm increasingly thinking that I might use the gsxr injectors - after all I already have them.

Yep, that was my theory. They should have plenty of flow for 200+bhp with a higher pressure.

quote:
Originally posted by chriscook
Neil didn't you get your suzuki rail modified to respace it? I've taken mine to bits and its trivial to extend the middle bits but you have flow in one end and out the other. Easy enough to machine the holes in but how do the ends stay in place?
Hope you don't mind me 'borrowing' your picture.

I had mine modified as a favour by someone who had done similar on his Westfield, so I don't actually know what he's done- I will ask...

Edit: OK, here's an answer from Michael:

"The middle bits of the rail that i lengthened were just direct copies of the original GSXR item but a a suitable amount longer, the ends were just drilled out then tapped and the ends were just glued in with an appropriate araldite. It is best to use a coarse thread on soft materials i think i used Whitworth as the tapping size was most suitable to the original hole needing only to be opened up slightly....
but again cant remember the exact size."

Hope that answers the question- this method is holding up ok on my installation...

Neil

[Edited on 30/11/06 by nre]

[Edited on 30/11/06 by nre]

chriscook - 30/11/06 at 07:04 PM

Thanks for that Neil. I will have to have a look and maybe even borrow some taps for the weekend

oioi - 1/12/06 at 01:59 PM

i used 330cc/min PICO injectors on my conversion. These are not cheap new (i think burtons sell them at 85quid EACH) but i got set of ebay for less than a hundred. i did not want to use a standard bosch injector as these would have been too tall and there wasa clash issue with the fuel rail and bonnet (early westie, engine quite far forward). im currently running about 215bhp, but may well go for something like 240 in the distant future. i think the 42mm throttle bodies will then be the limiting factor.

word of warning tho - the PICO injectors will NOT fit the standard gsxr fuel rail as they are shorter than the gsxr ones. I had a custom rail made out of billet aluminum - because i could