Injectors above the trumpets

[Driv3r]

Hi all, I'm planning to rebuild my tii engine and want to know if there are other companies that still machine ITB's with injectors on top of the trumpets (see sample attached google pic). Also wondering if there is a shop somewhere that could rebuild and upgrade my oem fuel injection pump to keep up with the performance upgrades. At this stage im just gathering info. 

 

[tzei]

https://www.saxonparts.com/product-categorie/fuel-system/throttle-bodies/

 

Some ready-to-go parts. ”Get quote” spells expensive?

[zinz]

Mmmmm... slide throttles. ?

 

 

 

[Driv3r]

40 minutes ago, zinz said:

Mmmmm... slide throttles. ?

 

 

 

 

Would the butterfly turn it into variable intake size for high and low rev? Same thing that was installed on F1 cars back in the day.

[gary32]

Love the look but the closer you get to direct port injection the more efficient. (less fuel separation)

Slide throttles have also been improved on also by the motocross world.

Nothing wrong with more power and better response.

The “rotating gate” only contacts the housing when fully closed. This means low friction.

[AustrianVespaGuy]

Safety is another thing to consider here; atomized fuel on the OUTSIDE of the throttles can get pretty exciting pretty fast if the engine backfires!

[TobyB]

Ah, that's true of any infernal combustion engine- it just looks cooler with external injectors.

 

I'll say it again, right here:

 

The only benefit to a slide throttle is if your throttle body size is restricted by a rule set.

Then the 'shutter' can get entirely out of the airflow.

 

If not, a butterfly works far better, and you just add 2mm to the body size to make up for 

the flow restriction.  But yeah, if you wanna squirt the fuel in from the back, too,

why not go full bling?

 

There are several benefits to hitting the hot intake valve with the injector-

at least one is increased performance.

 

fwiw,

t

 

[Preyupy]

The high mounted injector does work well at WIDE OPEN THROTTLE but is horrible under all other conditions.  With the engine running at 3000rpm at 25% throttle opening you can see the FUEL is hitting the throttle plate and running off the edge of the plate like a spilled beer running of the table.  Atomization works great as long as there is enough air flow to keep the fuel suspended in the air.
 

There is also the problem of fuel “stand off” if you are running a cam with a lot of overlap. watch a race engine on the dyno sometime and there is a HAZE of fuel outside of the velocity stacks when the engine is a bit “off the cam”.  Put the injector at the open end of the velocity stack and it will freak you out.  
 

Street engines should have the injectors behind the throttle plates. Race engines you give up drivability, fuel economy and emissions for that last 5hp. 

[Driv3r]

2 hours ago, Preyupy said:

The high mounted injector does work well at WIDE OPEN THROTTLE but is horrible under all other conditions.  With the engine running at 3000rpm at 25% throttle opening you can see the FUEL is hitting the throttle plate and running off the edge of the plate like a spilled beer running of the table.  Atomization works great as long as there is enough air flow to keep the fuel suspended in the air.
 

There is also the problem of fuel “stand off” if you are running a cam with a lot of overlap. watch a race engine on the dyno sometime and there is a HAZE of fuel outside of the velocity stacks when the engine is a bit “off the cam”.  Put the injector at the open end of the velocity stack and it will freak you out.  
 

Street engines should have the injectors behind the throttle plates. Race engines you give up drivability, fuel economy and emissions for that last 5hp. 

 

I’ve driven an e9 with m30b34 setup and had no problem at low rpm. Maybe it was setup differently but it did have injectors sitting on top of the trumpets. 
 

The sound and cool factor is my intention for this tii because it will be decorated and displayed at the auto warehouse bar that’s in the build. I’m going to have the faq to virtually build the motor for me by recommending the build list.

 

Another option would be to use Alpina ITBs but injectors are installed at the intake entry not on top. I’ve priced this setup and costs are in excess of $12K just to buy the ITBs. What do you recommend? Also, do I need different injectors and pump or my current tii injectors and pump suffice?

 

Cheers

[PaulTWinterton]

10 minutes ago, Driv3r said:

Also, do I need different injectors and pump or my current tii injectors and pump suffice?

 

I asked that same question in another thread.  But it was about the Aplina intake and whether or not my stock injectors would work. My reconditioned injectors can open at anywhere from 470 PSI to 540 PSI.  I like to sell balanced sets in the 470 to 500 range.  Above that I can't be sure of the performance of the standard pump.

 

I will say that injectors at 540 PSI (and above) have a more robust cone in density and life of the particles.  Meaning the particle cones are longer in length.