Re: [T3] Type three and Type 4 ECU's

["Craig Webb" <craig_webb@ntlworld.com>]

<x-flowed>Thanks for the feedback guys.  I'll try and answer you all in one go:

On Aug 25, 2005, at 13.06, Fess wrote:

> This may be a naive question, but isn't this the type of application where 
> you would want to go >to one of these fully tunable control units like the 
> megasquirt which has been mentioned a bunch >here?

Megasquirt is in the back of my mind and it may yet come to the front!  It's 
a very good system, but if I can get the D-Jet to work nicely (which it's 
not that far from doing), why change it?


On Aug 25, 2005, at 18.07, Jim Adney wrote:

> There's no load when stationary, so that's no real test. It sounds like 
> you've
> covered most of the bases, but I'd still run a gauge into the car and test 
> the
> pressure on the road. The screen in the tank could be clogged.

Tank was cleaned out during restoration, so it should still be good.  I've 
got a very large pressure gauge, so I should be able to mount it high enough 
and steal a quick glance backwards when driving!

> The first thing I would try would be 34 psi with the type 3 PS and brain, 
> from
> the same year as the type 3 wiring harness and throttle valve switch. I'm
> surprised that 34 psi is maxed out. I thought they would go much higher 
> than
> that.

This is where I'm at now with the results initially mentioned (I only 
briefly tried a type four MPS).  34 psi is not maxed out on the system, but 
after 35psi the injectors struggle to re-seat (something I been told from a 
D-Jet guru).  Stepping up an injector size is an option, but then I'd 
probably be very rich at low speed and about right at high revs.

> 1776 is only an increase of 11% over the stock displacement. I'm guessing 
> that
> the stock PS has enough headroom to tolerate that, but with your
> instrumentation you should be able to tell us, without guessing.

When I researched this engine, the common answer seemed to be "All you need 
to do is up the fuel pressure to 30-32psi".  My experience with this engine 
suggests that this would be seriously lean at speed (say 17-18 AFR).  The 
engine does run quite nicely now.  Idles well, pulls well and behaves 
nicely.  Occasionally get a bit of 'bucking' when driving slowly in first or 
second.  MPS seems to cope ok.  I'll post up the engine specs shortly, but 
its got a mild cam in it (CB Cheater - slightly more lift and duration, but 
not as much as say an engle W100) and an ISP over the top exhaust.

> I think we're all interested in how this turns out.

If you can hang on for a month or so, I'll get the fueling right!  I'm also 
looking into CDI ignition at the moment as well.  I'll post up my engine 
specs and things to look out for.


On Aug 25, 2005, at 20.07, Jim Adney wrote:

> People have occasionally added a resistor in series with the cyl head temp
> sensor and the ECU, but that's not the sensor that he wants to change here.
> He's talking about the pressure sensor, where we can't just add a resistor 
> in
> series.

Yeah, a resistor here would just richen up across the board.  Not what I'm 
after.


I'll try and get around to inspecting the type four system I've got in the 
garage and confirm it matches the type three unit I've got.  If so, I'll 
swap out the brain and MPS for type four stuff.  I'll run that for a bit and 
monitor the AFR's.  I expect the MPS will need some tweaking to get the 
right balance.  I'll post up some feedback when its running nice (might be a 
while as I've lots of housebuilding to do!).

Craig




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