Big injectors on a standard engine...advice please

[bananawhip 0]

I've got my inlet manifold off at the moment, so I thought now might be a good time to pop in the red-top injectors I'll need for my stage 2 charger I'll be fitting in the near future, how will it run?

 

Will it overfuel because the injectors are bigger or will the ECU still tell it to deliver the same amount of fuel regardless? Just plan on running like this for maybe up to a month

 

Any advice as always would be great

[Kevin Bacon 5]

Are they the 310cc red tops? I ran those in mine with the standard chip etc and drove it up to Stealth for mapping. It was a bit too rich when cold, but when hot the lambda trimmed out the fuelling. You could always put a 10K pot across the MAF output and ground to trim the signal down, which would work. Ask CrazyDave for more details!

[bananawhip 0]

Are they the 310cc red tops? I ran those in mine with the standard chip etc and drove it up to Stealth for mapping. It was a bit too rich when cold, but when hot the lambda trimmed out the fuelling. You could always put a 10K pot across the MAF output and ground to trim the signal down, which would work. Ask CrazyDave for more details!

 

They're whichever ones you get in a stage 2 Vortech set-up, not sure what the cc is. I've still got my 263's and some other bits fitted so I'm sure a little extra fuel won't be the end of the world. That last bit about the MAF made me go a bit cross eyed if I'm honest Kev, a bit above my skillset I think. When I fit the Charger I'm fitting the MAF upstream of it so I was under the impression it didn't need any modification.

 

I have been reading your VR6 FI everyday for about a week now just to get my head around it all :)

[Kevin Bacon 5]

Yeah, 310cc Ford Mustang injectors!

 

The 10K ohm variable resistor on the MAF output wire basically just fools the ECU into thinking it's getting less air than it actually is, so reduces the fuelling accordingly, which if you've got bigger injectors, works nicely :D

 

I didn't do that when mine was S/C'd though. I may have even fitted a 3 bar regulator in place of the 4 bar one come to think of it, which will reduce the fuelling a bit too.

[bananawhip 0]

Thanks for the good advice as usual Kev, I'll keep an eye on it and if it's overfuelling I'll try popping in a 3 bar reg just to bring it down a bit. Only needs to be a short term fix.

 

No doubt I'll be asking a few more questions when the Charger arrives but for now that clears things up a bit :)

[poll250 0]

Bit of a thread resurection here.

 

I still haven't fitted my Rotrex, but am thinking about doing it in the next couple of weeks. Just starting to do the preparations like extending the MAF cable, fitting the meth injection etc

 

I've got a set of Green tops ready to go in. Could I stick these in before I put the charger on and run it for a couple of weeks? Would it cause massive overfuelling on idle?

 

I read about using the 10k resistor, would this be the kind of thing I should use: http://cgi.ebay.co.uk/10K-Ohm--POTENTIO ... 62ff74f24e

 

I assume I'd wire that into the MAF output wire somehow, and then adjust resistor until the car idled properly?

 

Thanks for any help as usual.

[Kevin Bacon 5]

Motronic automatically trims the injector duty to MAF flow, so that works on OBD2 with a 4" MAF housing because it has more lambda adjustment.

 

Indeed I ran mine like that for a while myself, but sometimes the ECU runs out of lambda adjustment (25% max) and you can end up being too rich at certain rpms and loads, but overall is drivable. Not the smoothest or most responsive, but drivable - to the dyno :wink:

 

Never tried it on OBD1 though, but if you can graft on a bit of 4" drain pipe to your MAF (if you have the older 5 pin one) it should work. I've seen that done a few times on VRTs.

 

With the stock 3" MAF, then yes, you need to fudge the MAF signal to fool the ECU into thinking it has a bigger MAF. I remember Crazy Dave saying his 10K pot method was pretty much at the limit with the Saab 360cc injectors, so it might not work with 440s.

 

And whilst on the subject of the Green tops, I would get them flow checked before putting them in the engine. They are notorious for being poor atomisers at low duty cycles and often come in bad batches, so 1 or maybe 2 of the 6 might dribbel and leak instead of being off.

 

The Bosch "Green Giant" 440cc (from the Volvo T5R) is a better bet, especially as the older EV1 440s have been obsolete for some years now.

[poll250 0]

Thanks Kev,

 

The more I hear about the Green tops the more I wish I'd just got a nice set of 360cc reds, would have been a lot easier and cheaper.

Maybe I'll try swapping them for a set if anyone is keen!?

 

I guess I might just have to bite the bullet and take my car to D&G to get the charger fitted and setup, I don't know how confident I feel messing about with £2000 worth of supercharger by myself. :confused4: