What injectors to use

[URSIMPO]

I used Siemens in the end. My car when warm stumbles at idle and causes me to stall sometime at the lights (most embarrassing), but never when the car is cold will it do this. Could the injectors be at fault?

[S2central.net]

Depends who mapped it and whether they tweaked all the right parameters for non-standard injectors. If that was done correctly then maybe there is something up with a temp sensor or idle valve that is playing up - or maybe idle switch in the throttle pot is misbehaving.

I could look at the chip contents if you want a view on whether enough was done to accomodate the monster injectors.

[URSIMPO]

Mineha (forgive spelling) at MRC mapped it a couple of years ago. Would the temp or idle valve show up on vag com? I'd had it plugged in and nothing showed, I even changed the lambda sensor just in case...

[Thuppu]

I have heard that Siemens Deka 650cc is not ideal for S2/RS2 motronic as the latency adjustment cannot be made perfect. I want to play with a set sometime to see if this a minor niggle or major drama.

Ok, what would be the optimal injector choice for 500-600hp with motronic? Does Bosch have any plug and play choice in the same size as Deca?

[S2central.net]

Mihnea knows this stuff better than me so it should be fine unless he overlooked something - or the injectors are a different variant than the specs stated. Some specs are hard to find... and there is this doubt that Siemens 650 can be properly accomodated by S2/RS2 motronic anyway - When did the warm idle issue start happening ?

Unlikely for temp sensor or idle valve to show up on vagcom... it could be a sticky valve - carb cleaner does them a treat. The other possibility is unmetered air at idle/vacuum... Tell me what you see in VAGCOM on Group 0 at warm idle.

[URSIMPO]

Thanks Paul, I'll try the carb cleaner first off, and get it plugged in to VAGCOM if the problem persists.
Also as an fyi, when I was in the mountains (Stelvio to Davos), at the high altitude the car wouldn't start unless I applied throttle. Don't know if this means anything?

[S2central.net]

That is interesting - did it always idle funny after the injectors were fitted - or is just a fault that began more recently ?

[A80Avant]

it shouldnt stuble. i currently use 630cc injectors for the 3076R turbo (but with VEMS) and i have no issues with idle whatsoever. I know the ISV is working though.

[URSIMPO]

That is interesting - did it always idle funny after the injectors were fitted - or is just a fault that began more recently ?

From memory it didn't do it straight away, maybe a month afterwards? As long as I keep blipping the throttle it's ok, but at traffic lights, it sounds like I want to race everyone

[Thuppu]

What do you think about these injectors? Bosch EV14 5pcs flow-matched kit, 750cc/min 3bar, 12.8-15.5 Ohms.

[prj]

What do you think about these injectors? Bosch EV14 5pcs flow-matched kit, 750cc/min 3bar, 12.8-15.5 Ohms.

Don't think that will work on motronic... need to talk to porkkis about it.

[Thuppu]

If I remember right the bigmaf testcar he has tuned have EV14 injectors. Seems also to work fine on 2.7Bit and 1.8T. Of course you need USCAR -> JET adapters for the connectors.

[prj]

The 550cc EV14 will be fine.
But the 750cc - I don't think motronic has enough resolution for that to run at idle.

[Thuppu]

Ooh, I see. So they can be too big...

[Thuppu]

Ok, I missremember, it's 630 dekas on his testcar. So, the injectors should be max. 550cc at 4bar. There is not so much options here. The 440cc greentops give ~510cc at 4bar so maybe 500hp would be the max power you get with them..? 550hp no.

Found these kind of specs for the Greentops(Bosch 0 280 150 558). Don't know how accurate they are?

441cc / min flowrate = 42 lbs / hour @ 39.15 psi (=2.7 bar)
465cc / min flowrate = 44.3 lbs / hour @ 43.5 psi (=3 bar)
537cc / min flowrate = 51 lbs / hour @ 58 psi (=4 bar)