V2Rocket

Economy gauge is load vs injector duty cycle.

Ish_944

Thanks guys!
So how does one correct it for new injectors? Do I need to get into the ECU software to make the square wave wider for a given injector duty? (I've got stock Turbo ones now.)

Edit: Oh, wanted to ask this too:
I've seen the gauge needle flapping around and sometimes consistently reading about 2x as much as it should have. Then it just randomly fixed itself.
Both with the factory DME & engine and also with the new stuff. Do you gents have any idea how this is possible?

Noahs944

So cost of conversion update. Where am I at right now? Wilson is driving like a champ still with the 8 valve engine. On the other thread (16v into a 924?) someone mentioned "for that amount of work you could put in a turbo or 3l".

Right now I'm thinking the same thing. But I'm not turning back, I have committed.
Rebuilt head $2000 cdn
Brand new front cam timing cover $280 cdn
Distributor/rotor/leads $200 cdn
injector ballast -used $100 cdn
7 pin female bosch connector (thank you odonnell) $30 cdn
Resurface flywheel $100 cdn
16V Air filter housing $160 cdn
S coolant hoses, engine bay $160 cdn
---------

$3000 cdn/$2325 US

OTHER EXPENSES: Need a seal & bearing rebuild kit (a complete kit is about $1100US not including water pump/rollers & belt and some other things). Also need to figure out if I can adapt my stainless fuel lines also.

And do I hot rod this engine now or wait? I don't think I have a choice but to wait because I can't even afford the bearing & seal kit right now.

Honestly this idea started out with a different plan.

V2Rocket

You should have adjusted the injector sizing scale in the DME when you switched injectors.
The 951 units flow ~50% more than the 944 ones...but they are also a weird resistance.
I would try to find 36-42# injectors off another car with the same resistance as the 944 DME (~2.4-2.8ohm) to make everything happy...

odonnell

This is a good starting point: http://www.polog40.co.uk/article_injector_table.php

It looks like there are multiple options for Bosch injectors that will meet those criteria. My experience is that most Bosch injectors have the same physical dimensions. I was able to find dozens of retailer options offering 1-5 year warranties on rebuilt and flow matched injectors for under $100 a set.

Humboldtgrin

You can use high impedance injectors with the turbo's DME. Or use low impedance with a resistor in line. See Clarksgarage write up on it. High impedance would be the way to go. Much easier on the DME drivers for the injectors. Timing would still be a huge issue.

Noahs944

What do the oem "resister ballasts" do ? Limit voltage for some reason?

odonnell

Stock 8v cars don't have ballast resistors.

Basically the ballast resistors reduce the current that the injector drivers have to put out. If you've ever heard "high z" and "low z" injectors come up, this is the difference...those resistors just impede the control signal more. The reason that's useful is a whole other topic all together... what matters is what you ECU is designed to control. The DME works with low-z (no ballast resistor) injections for the 8v.

I'm running high z on my car (12 ohm a piece) because my ECU mandates that each injector channel is no more than ~5 ohms, and 2x 12 ohms (2 injectors per channel) in parallel is 6 ohms.

Raceboy

I can run any injector type I like with any configuration by just changing few parameters in tuning interface, couple that with the fact that factory ECU's leav a lot power to the table and I see no reason why you would even want to mess with different DME's..

Ish_944

I've got the Augtronic, so I've to check if it can be adjusted for the econometer.

Humboldtgrin

The turbo DME uses 4.5 ohm injectors. Not many injectors are made at that resistance. So if you use a turbo DME and low impedance injectors you must install a 1 ohm resistor on each batch fire power wire going to the batch fire injectors. If you use high impedance injectors the drivers work much less and don't get hot because less current is needed to open these injectors. The regular 944 uses low impedance injectors. Only the turbo uses 4.5 ohm injectors. In fact I have never seen another vehicle with 4.5 ohm injectors installed stock other than the 944 turbo.

jeffro951

Hey Noah I see you picked up the air box today. If you still need that wire harness you mentioned let know I am pretty sure I have it I just have to dig through the 3 tubs of wire harness that I have.