Highest Boost On Standard Jetronic?

[Saveit 0]

Hi,

 

Was just wandering, what is the highest boost pressure you can do on a daily driver reliable engine with a turbo running standard jetronic (yes i know, sucky) management? I am not after some incredible figures or anything, just an easy boost in power? How much can i go using jetronic and which injectors would be suiteable for a slight power increase - GTI6?

 

Stefan

[richsmells 2]

Running jetronic with an AFM and larger injectors would cause it to overfuel at low revs. With mappable management, the fuel can be accurately controlled at any engine speed.

 

I think the closest you'll get on Jetronic is using a TT style 5th injector setup. Normal fuel off boost, plus additional from the 5th injector on boost.

 

IIRC TTs ran lower comp pistons, whether you'd get accurate enough ignition control on a standard compression engine is another matter!

Edited May 19, 2009 by richsmells

[Tom Fenton 1,542]

Jetronic has no way of compensating fuelling for boost pressure so will not run properly on boost.

[Saveit 0]

Is Motronic any better fueling wise?

 

But how reliable is the 5th injector setup? Can it be used and will it run properly?

[mattbenselin 0]

Why not use the loom and management from a 406 8v turbo, or the whole engine?

[bales 1]

I don't know how you would expect it to run on the standard engine,

 

Firstly as has been pointed out that management is purely based on air mass and not a speed/density system like on the 2.0T or on a gti-6 so wouldn't be able to differentiate between boost and normal so you couldn't fuel it.

 

5th injectors are at best a bodge which is literally just on off so its not the most tractable or smooth of methods. You haven't mentioned lowering the compression, and as you have such poor control over the ignition anyway then you won't be able to put much boost through it, maybe 5-6psi at most.

 

So personally I wouldn't have thought it is worth the hassle as it will probably blow up anyway if it gets too hot or starts to go lean. Why not consider the 2.0T or what Tom Fenton has done for his conversion - i.e use the best of both worlds with parts from both engines.

 

So for the 160ish bhp you might make you may aswell just stick an mi or gti-6 in....

[danpug 1]

Why not use the loom and management from a 406 8v turbo, or the whole engine?

 

As henry yorke has done with decent results.

[jackherer 543]

5th injectors are at best a bodge which is literally just on off so its not the most tractable or smooth of methods.

 

Thats not strictly true, the TT fifth injector had a controller and later copies of the TT setup I've seen have used MF2 controllers IIRC. Thats not to say they aren't a bodge as such, its 2009 and things have moved on a lot from the 80s/90s when TT were doing these conversions to 205s.

[Henry Yorke 269 3 Cars]

The TT set up also used a modified distributor to retard the ignition too IIRC and a 5th injector stuck into the throttle body on an MF2 set up as has been said.