Uprated Injectors Vs 5th Injector (turbo)

[Nathan 0]

Hello,

 

I've recently purchased a turbo technics kit which will be going on to my 1.6, the engine is currently undergoing a leak down test and providing the results from this aren't too scary I hadn't planned to do much to the internals and compression ratios just yet (I'm hoping that with decent fueling and cooling I can keep detentation risks to a minimum). Boost levels will also be kept relativey low (approx 10psi i reckon.

 

I plan on using a megasquirt v3 ecu to take car of fueling/ignition, but the turbo technics kit reatins the standard injectors and adds a seperately controlled 5th injector, this seems quite a crude method to me, I'd rather run 4 correctly speced injectors. So that being the case what spec injectors do I require?

 

I'm hoping for 160bhp ish, is this going to be achieveable on completly stock internals?

[TEKNOPUG 3]

You only need a 5th injector if you use the standard ecu. If you use the megasquirt then it can be mapped properly to allow for the turbo and hence you will only need 4 injectors, albeit with higher flow rates.

 

Run a search for injectors - it's been covered many times.

 

Standard 1.6 TT makes 160bhp, so Id expect you to see considerably more with properly mapped engine management.

[pdd144c 0]

Rover T16 turbo ones are good. That's what I used on my old TT.

[welshpug 1,657]

a bit of guesswork i know but doesnt the TT use a standard injector for the additional fuelling?

 

if it is then divide the flow rate by 4 and add the figure to the std injector, maybe add a little to compensate for being able to run more power with mapped ignition?

[TEKNOPUG 3]

Best thing to do is have a look at some of the flow rate spreadsheets (Smckeon has a link to one in his sig). Look for injectors that flow enough for 200bhp+ (in a batch of four) as that will allow you to run them at a safe 80% on your engine.

 

Basically ones with a flow rate in excess of 300cc/min.

Edited April 18, 2007 by TEKNOPUG

[mak 0]

a bit of guesswork i know but doesnt the TT use a standard injector for the additional fuelling?

 

No, they're green tops and IRC flow slightly higher than std

[Doof 11]

Is it dangerous running a 5th injector at all? Because if the 5th injector died then suddenly everything is running lean and probably detonating?

 

Equally if one of the normal injectors fail that cylinder will run lean as it will only be getting fuel from the 5th injector.

[welshpug 1,657]

Is it dangerous running a 5th injector at all? Because if the 5th injector died then suddenly everything is running lean and probably detonating?

 

Equally if one of the normal injectors fail that cylinder will run lean as it will only be getting fuel from the 5th injector.

 

 

yes, but that could happen on any engine setup not just that one.

[Doof 11]

No because with a normal setup of 1 injector per cylinder it would just drop that cylinder....but then whats the chance of an injector failing completely, it would probably just not work 100%...and these things are mega reliable anyway. Ok i'll shut up and do some work.

[TEKNOPUG 3]

Yep, to an extent. But I know of at least one TT that lunched a piston because one of the normal injectors failed (not the 5th injector).

Its actually less of a danger with a with the 5th injector (or at least its less of a danger compared to the 4 normal injectors) as it only fires when on boost, so you could still run the engine safely if it did pack up (for means of getting home) without causing any damage.

 

Its an old, antiquated system (think clockwork compared to digital) but it works and its reliable as there arent any clever parts to go wrong. Id estimate that ditching the 5th injector/afm/dizzy for 4 injectors/coil/mappable ecu is worth at least 20% increase in power/torque on an otherwise standard engine, judging by most peoples results.

[Nathan 0]

Cheers for the advice so far, I can get hold of a set of Pico injectors cheap, these are around 400cc and also a nice custom fuel rail to mount them in, but would they present problems being that high a flow rate? They were originally on a 1600cc motorbike engine (busa) which was probally around 210-220 bhp. But with them being desingned with bike enigine use in mind I'm not sure they'd be suitable???

[mak 0]

Is it dangerous running a 5th injector at all? Because if the 5th injector died then suddenly everything is running lean and probably detonating?

 

In theorey it is, but in reality its not. If my 5th injector packed up I would know with in a couple of seconds!

[cybernck 402 1 Cars]

how exactly does the 5th injector work in the TT setup?

 

i mean, what's the "mapping" controlled by (what are the inputs)?

 

 

also, is it plumbed in in serie or parallel with the main injectors

(is there are T before the main fuel rail and then another after it

or does the fuel hose go to the 5th injector and then to the main

fuel rail?)?

 

 

thanks .

[Mad Professor 7]

Just a quick word of advice regarding injectors, Try not to go over big, as at low rpm's & your idle will start to suffer (being lumpy).

 

I am running 4x 390cc/min injectors on a 1.9 Turbo running 1bar, and that is more then anuf, and even thease when the fual map was dialed in, give me a very low 1.5-2.0ms injection rate at 950-1000rpm.

 

So I would advice to look at what power you are aiming for and get some injectors that would flow to this, and add 10% to 15% on top just for safty.

 

100hp = 4x 158cc/min.

150hp = 4x 231cc/min.

200hp = 4x 305cc/min.

250hp = 4x 389cc/min.

 

Best Regards.

[petert 586]

I am running 4x 390cc/min injectors on a 1.9 Turbo running 1bar, and that is more then anuf, and even thease when the fual map was dialed in, give me a very low 1.5-2.0ms injection rate at 950-1000rpm.

 

That's a function of the quality of the ECU and injector dead time. A Motronic or Autronic would not have a problem with that.

[TEKNOPUG 3]

how exactly does the 5th injector work in the TT setup?

 

i mean, what's the "mapping" controlled by (what are the inputs)?

also, is it plumbed in in serie or parallel with the main injectors

(is there are T before the main fuel rail and then another after it

or does the fuel hose go to the 5th injector and then to the main

fuel rail?)?

thanks .

 

Run a search on posts on Matt Cony with Chipwizards in the thread. There is a very detailed description on there.

 

In essence, there is a box that has an input and an output. The input is taken from Manifold Air Pressure (boost) and has a dial that you can adjust the threshold (basically the level of boost pressure that you want to see before you fire the 5th injector). The output is for the 5th injector and this too has a dial which you can adjust to alter the amount of fuel injected. Advanced stuff eh?! There is an additional fuel line which runs from the fuel filter to the injector. On a normal fuel filter the connector that the fuel line goes to just has one horizontal hole. On the TT it is longer and with an additional horizontal hole above to connect the second fuel line. Thats pretty much it. Also, the is retard capsule in the dizzy to adjust the ignition advance to suit. This is often overlooked as people tend to get all worked up over increasing the fuel supply. Its actually the correct adjustment of the ignition that will give you most gains in performance rather than the correct levels of fueling.

[cybernck 402 1 Cars]

ah thanks, thought it would be like that (can't be much different anyway ).

 

however, the reason i asked this is to see wether the pulse width, once on boost, is fixed in the TT setup.

 

appears that it is.

 

 

as for the plumbing, if i got you right, it's in parallel with the main injectors (sort of) and doesn't have the fuel return:

 

.--=i=i=i=i=-[FPR]---

`--=i=

 

thus having the main FPR keeping it pressurised.