On problems with LE Jet and performance upgrades

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Disco Inferno
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Joined: 01 Feb 2007 02:44 pm
Location: NSW, Australia

On problems with LE Jet and performance upgrades

Post by Disco Inferno » 15 Dec 2007 07:45 am

Apologies in advance if this has been discussed/debunked previously.

Now, I know it's the general consensus that LE-Jet sucks for intake/exhaust modifications.
For example, freeing up the intake, adding a more agressive cam, and putting a low restriction exhaust on will make the car run lean, even to the point where power will decrease in some cases compared to stock.

What I don't understand in this case, is why the mixture adjustment on the airflow meter has not been employed to add the required extra fuel?

I thought, at first, that it was a base idle mixture screw, but on further head scratching and digging for information it seems it does, in fact, directly adjust the mixture across the rev range, somewhat like the mixture screw on a carburetor.

So basically, have any of you guys tried this before? If not, why? Looks to me like the LE is a lot more tunable than y'all think.
'89 740 Turbo HP - 13.5psi, 3" turbo-back exhaust, big intercooler, iPd Turbo cam, huge K&N filter - 14.6 @ 93.3MPH
'85 360GLT - still trying to stop the rust!

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foggyjames
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Post by foggyjames » 15 Dec 2007 11:47 am

As I understand it, it does mainly affect idle...or thereabouts. More to the point, you'll typically need a lot more enrichment at the top end than you will down low. Given that accurate AFRs are critical to achiving both power and reliability, and that LE-Jet pretty much seems to suck anyway, I'd get shot of it ASAP if you're planning to tinker.

cheers

James
VOC 300-series Register Keeper
'89 740 Turbo Intercooler
'88 360 Turbo Intercooler
'85 360 GLT
'81 343 GLS R-Sport
'79 343 DL
'70 164
...and some modern FWD nonsense to get me to work...

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Chris_C
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Post by Chris_C » 15 Dec 2007 06:52 pm

Andy found a schematic of LE a while ago, it's basically a set of resitor capacitor networks to sort out timing depending on revs and flappy paddle from memory. Without looking at it again, I'd assume Foggy is right, that one screw can't accurately change the fueling for all rev/load combinations in the way a new cam etc would require :(

This is also the reason that I don't think carbs for a DIY tuner are a good idea, not only do you need to know where to fuel, but you need to really know your stuff to get them jetted properly across the rev range, not an easy job at all!
'89(G) 340 GLE B172k
'03 S60 D5 SE, '91 (J) MX5, 1954 Cyclemaster
Ex:
'89(F) 340 GL F7R (ex B172k) - Fake -> SBKV 300 Runner Up 08, 12; '91(H) 340 GL B14.4E - Kar; '88(F) 360 GLT B200E - Jet -> BKV 300 Runner Up 09; '89(G) 360 GLT B200E - Beast

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