Injector location (ITB)
 

Hi all,

Long story short, while turboing my BP I managed to find a great deal on some TWM ITB’s and thought “yeah, I’d like to try going slow and sounding cool” so I’m going to give them a go and will possibly go back down the turbo route at some point.

Now, the TWM’s came with some old Bosch injectors (280150728 250cc EV1) which are in the ITB’s (as per pic below):
https://cimg3.ibsrv.net/gimg/www.mia...54bfe2527f.jpg
You can see exposed holes above where the TWM fuel rail and injectors all fits and looks quite nice.

While acquiring my tubro bits I grabbed some new 750cc FF injectors which I know will be good but, from what I can tell I can’t adapt to the TWM rail position (I’m new to injectors, correct me if I’m wrong) and would need to use the factory location.

My question is, given I’m about to do the wiring would it make that much difference using the factory location vs. TWM’s? Given I may go back to turbo at some point, it’s not a fancy-built NA motor and I know the FF injectors are tested and I have new plugs, it makes sense to me but, this is outside my scope of knowledge.

Guide me pls

I’m unsure as to why you would want to be closer to the throttle bodies other than perhaps better atomization of fuel.

I think it would be better to be closer to the motor. Mainly because of less fuel being deposited on the intake manifold, which could make your acceleration enrichment (normal AE and EAE if you’re messing with that, the effect would be more evident in EAE if I had to guess) easier to tune/lower values.

all of this is speculation for the most part though, I’m not the most certified person on here haha

I'd run the injector in the factory position and leave the ITB injectors in their mounts with no fuel or electronics to them.
I wouldn't hard modify (ie JB weld or tig welding) either injector location.

I have a perfect VVT head that the previous owner JB welded the stock injector mounts closed. If I cannot remove said JB weld the head is trash for use with anything but ITBs...

Think about the next guy buying your parts, don't hard modify if you can avoid it...

Wiring for either position should be identical.

Cheers guys, I'm going to go with as suggested. Chances are I'll go back on boost soon anyway so nothing perm is def the best way I think!

Just to clear things up a bit, here's a snippet from Jenvey:

"For performance at low RPM, economy and low emissions the injector needs to be close to the valve and firing at the back of the valve head. This is the favoured position for production vehicles.
For higher RPM (very approximately 8,000+) the injector needs to be near the intake end of the induction tract to give adequate mixing time and opportunity. The higher the RPM, the further upstream the injector needs to be. As a result, use of speeds above approximately 11,000 RPM may give best results with the injector mounted outside the inlet tract altogether (see our remote injector mounting). It is common to fit both lower and upper injectors in such a system to cover starting and low RPM as well as high speeds."

If this was a built, high revving NA monster, you'd want to move the injectors to the upstream position, but our engines don't like 8K+ in stock form, so the factory position is best for your use case.

Just for fun, here's a remote/outboard injector setup you'll see on all out high RPM ITB setups

https://cimg4.ibsrv.net/gimg/www.mia...5e729aaa4a.png
https://cimg6.ibsrv.net/gimg/www.mia...9d2a5fc614.png