Throttle Bodies And Double Injectors

[DamirGTI 327]

Hi !

 

Anyone try some experiments with this :

 

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Thanks !

Damir

Edited March 28, 2007 by DamirGTI

[smckeown 1]

am sure thats been posted before. Some people on the forum have experimented with double injectors already. I'm planning on testing double injectors on my 8v rebuild on the RR. Should be up and running in next few weeks..

[dee205 3]

It would probably be a pain to setup but well worth it.

[28CRAIG 2]

There has been a few post on here before about running 8 injectors it seems there is little point unless you have a race car and you need the extra edge. What would they be on and what would it be used for?

[Sandy 189]

That's Colin's car, who is an occasional poster on here.

 

I'm a big fan of twin injectors. The basic principle for getting more power, is to marginally improve mixing and to some extent inlet charge cooling too. Although experimenting with a single injector position might well get nearly the same results.

The real benefit is for cars that aren't being driven at full chat all the time. Using two sets of smaller injectors staged (second set switched on duty cycle ideally) means that normally you'll have the inner set injecting onto the back of the valve with long duration (ideal at low rpm and part throttle); then as air speed and volume increases, the second set are switched in when needed to provide the extra fuel needed, injecting it upstream as well as the inner set, giving good mixing.

There are two hazard issues which can spoil the fun. Firstly, a friend of mine saw a 205 in the Toyo series catch fire because it appeared to be running two sets continuously and the fuel from the outer set was being blown out of the tracts, then caught fire in the filter. This is why they have to be properly staged. the second issue is securely mounting the outer set so that the fuel rail doesn't come free. Colin had his first set up nearly go up, when the welds in the trumpets (early Jenvey items) cracked and the fuel rail came off. Thankly it wet itself but didn't catch fire.

 

IMO twin injectors are more relevant to cars which have a wide range of function than single minded race cars really.

[pdd144c 0]

The Toyo car in question only had 4 injectors Sandy, positioned in the bell mouths. Experimenting with a single injector position will give very good results

[taffycrook 2]

Not a lot of point to 8 injectors, you can correctly size and control an engine with 4 injectors now.

Think about big power 4 cylinder cars how many have 8 injectors?

Even if you had 300 bhp there is an injector that can handle this and let you have a smooth ticker and part throttle response.

 

A few years back this was not the case and the case for 8 injectors was stronger, there can be some plus points but if you can get the fuel in mix it with air and set fire to it thats all you need.

 

desiel cars have fuel coolers to keep temps under control due to higher pump pressures this may be a good idea. But I doubt petrol gets hot enough in the rail to effect performance.

[smckeown 1]

taffy - how can you say there's no point to 8 injectors, that doesnt make sense. We know that the further away from the valve the injector is, the better fuel atomisation, therefore the more power. However, you can't always have the injector squirting when it's say outside the bellmouth (i.e. low speeds/revs). So logically it makes sense to have inner injectrs at low speeds and outer at high.

[petert 554]

Not a lot of point to 8 injectors, you can correctly size and control an engine with 4 injectors now.

Think about big power 4 cylinder cars how many have 8 injectors?

Even if you had 300 bhp there is an injector that can handle this and let you have a smooth ticker and part throttle response.

 

This is because the top end ECU's (Motec, Autronic etc.) can control a big injector better at idle. It's a case of you get what you pay for. The big hp engines still have the injector mounted in the top of the trumpet however. So "idle quality" is somewhat different to a road car. As Sandy pointed out, eight injectors are still great for naturally aspirated engine with a wide power range.

[DamirGTI 327]

am sure thats been posted before. Some people on the forum have experimented with double injectors already. I'm planning on testing double injectors on my 8v rebuild on the RR. Should be up and running in next few weeks..

 

Please be kind and post some results of that project when you finish

 

As i understand it isn't so much power gain with this double injector mode but it's a cheap way to get few bhp more with all other modifications on the engine

 

Damir

[Sandy 189]

Digressing slightly onto the subject of using accurately sized injectors.... I've just switched my Trio (~230bhp) from 400cc (new) to 265cc (used) injectors and the simple fuel delivery (cc x duration) at full throttle is about the same, but from about 15-40% throttle, the simple fuel delivery is reduced by 10-20% and at cruise it's 20-30% reduced for the same AFR reading! Idle quality is similar, but smoothness is noticeably better and it's not wetting out the inlet like it was before at idle. That's a huge improvement in my book and once this tank of fuel is finished I'll have an idea of the MPG effect. I've always found mapping easier with well chosen injectors and twins take that principle a stage further.

[taffycrook 2]

taffy - how can you say there's no point to 8 injectors, that doesnt make sense. We know that the further away from the valve the injector is, the better fuel atomisation, therefore the more power. However, you can't always have the injector squirting when it's say outside the bellmouth (i.e. low speeds/revs). So logically it makes sense to have inner injectrs at low speeds and outer at high.

 

The point is if you can use 4 injectors and not have the added cost and complication of 8 injectors whats the point.

There are plenty of 4 pot 100 bhp/ltr NA cars out there now none have 8 injectors.

You can position the injector to have good low speed control as well as big power. Correct fuel atomisation is easier to achieve at 3 bar as the fuel droplets are smashed into the manifold floor or back of the inlet valves.

The big benifit is the cooling of the charge air you get with the injectors further away from the combustion chamber.

 

I prefer simple solutions!

[eeyore 0]

hey thats my car! The major benefit of 8 injectors that no one has mentioned yet is, you can use 8 standard injectors and never run out of capacity, this is a huge advatage to me being very frugal!

[DamirGTI 327]

hey thats my car! The major benefit of 8 injectors that no one has mentioned yet is, you can use 8 standard injectors and never run out of capacity, this is a huge advatage to me being very frugal!

 

You mean this blue gti in the magazine that i posted ? nice !

 

Are you running the same setup now or maybe some new mods on that system ? don't know from which year was this article in magazne

[eeyore 0]

it was about 1999/2000.

that actual car got destroyed in a accident! and was replaced with a light blue almost idenitical car.

the car is now in France and im building a new one similar but hopefully quicker!!

its still running the same setup but now with a 2.2 engine. making 240bhp/205lb ft toque, the same 8 standard mi injectors coped easily with the extra power.

Edited March 29, 2007 by eeyore

[pip470 61]

I have seen a lexus engine on a dyno with one set of injectors in the usual position on the manifold and a set pointing down the trumpets. Only one set at a time were used and the power and torque graths compared. The inner ones provided excelent top end power with not a lot below 6500 and when changed over to the ones squirting down the trumpets they gave a great spread of power from 3500 but lost a lot at the top end. The dyno operater told me that was the exact opposite as to what he was expecting. More development has to be done on this yet but im just giving a back to back test i have witnessed. Cheers Phill

[Malachy 0]

im using staged injection in my turbo build

200cc/min primaries with 360cc secondaries kicking in when on boost.

[DamirGTI 327]

it was about 1999/2000.

that actual car got destroyed in a accident! and was replaced with a light blue almost idenitical car.

the car is now in France and im building a new one similar but hopefully quicker!!

its still running the same setup but now with a 2.2 engine. making 240bhp/205lb ft toque, the same 8 standard mi injectors coped easily with the extra power.

 

Yes i remember having that article for some time

 

good luck with your projects !