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SU EFI Manifold Update


z-ya

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If boring out the horns is too risky, and you dont want the hoses and clamps showing, fab up a couple of short aluminum collars from some pipe or large rod, fit to the TB's and the horns, and press them on. Then set them with a couple of grub (set) screws (with locktite). You dont want them coming loose and getting sucked in, so a press fit might be the best.

 

The IAT sensor really does not need to have a huge influence on the FI system, especially if you are going NA. I would think that fitting it anywhere in one of the TB's or runners would suffice if an airbox was not being used.

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I was thinking of popping the freeze plug from the left end of the balance tube (the right end will go to the brake booster) and taping it to 3/8" NPT for the IAT sensor, but I'm concerned about there not being much flow through the balance tube, which could cause inaccurate IAT compensation.

 

Pete

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You are better off just making a bracket near one of the horns to mount the IAT sensor for underhood ambient temperature compensation. If it's in the manifold it will heat soak, and the balance tube is not moving a lot of air as you mentioned, so it will be worse there.

Look at the larger ports in the TB, there should be something you can stick the fine-wire GM probe into the airstream without much ado. Like remachining one of the heaters on the top where the return spring bracket mounts. A simple block there with the appropriate holes to refix the bracket, and a hole to the top of the T/B's airstream would do nicely.

 

Have you checked out a 240SX for their Airbox Air Temp Sensor? It is VERY small, and mounts with two screws on a diamond shaped metal backing. Two wires to lead out. Spotface a flat flange mount just about anywhere on the body that will let the sensor poke through and you're in business. It's so small, I would almost bet you could hide it UNDER one of the metal heater bodies on the top of the TB and just have the wires and connector hanging out...

 

If you were into hiding things, that is. The flange on the 240SX sensor for the airbox has holes very close to some of the original thermostatic elements in the 73/74 air cleaners. If one was so inclined to use it in one of those...without a lot of hacking... (whistles innocently...)

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  • 3 weeks later...

Here is the latest. I've mounted the IAT in the throttle body using Tony's suggestion. Worked out amazingly well. The butterfly opens away from the sensor, so there will no interference.

 

Also notice the mod to the 240SX TPS mount. The ZXT TB TPS mounting holes are spread apart more than the 240SX sensor. So I used a ZXT sensor plate, and mounted the 240SX sensor to it.

 

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are you going to mount an IAT in each throttle? You could log it using megatune and see the difference between the air temp between the front and back cylinders.

 

...it would only be for the geek factor though.

 

As far as I know, MSII only supports one IAT sensor. You would have to rewrite some embedded code, and then would you control the compensation for each injector bank that is associated with a TB? There is a balance tube, so I think it would all average out anyway. Now using both for monitoring temperature and only one for air temp compensation, that would be interesting. Still would require code changes. Of course an additional ADC would need to be available on the processor anyway (never mind DB37 pins).

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I let the comment slide at the time, but now being in Morocco and near midnight the question begs (BRAAP be Praised):

 

"What praytel, would they need freezeplugs in the balance tube for?"

 

Casting Plugs...

Core Plugs...

 

But....freezeplugs Pete?

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I let the comment slide at the time, but now being in Morocco and near midnight the question begs (BRAAP be Praised):

 

"What praytel, would they need freezeplugs in the balance tube for?"

 

Casting Plugs...

Core Plugs...

 

But....freezeplugs Pete?

 

Wow, it took you two weeks to discover that in my post? Tony, I think you are slipping a bit in your old age. And I thought you of all people would know that the air up here in NH freezes solid, so that freeze plug is there to prevent the balance tube from cracking due to the pressure of the freezing air. I've personally seen them pop out and fly across the room on a cold enough night. Geeze..... :mrgreen:

 

I'll be in Copenhagen next week so we'll have to see what my posts look like then... 8^)

 

Pete

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Got her running with MSII. Was runnig MS-Extra last year. EDIS isn't advancing the timing for some reason so it is running in limp-home mode (10deg advance).

 

http://upload.streetfire.net/video/Dual-Throttle-Body-Datsun_501660.htm

 

No Fair you got yours running before mine!!

I had the same problem with my install on the EDIS. Had the saw wire in the wrong spot. My 49 year old eyes let me down!

 

Great work Pete!

 

 

Derek

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No Fair you got yours running before mine!!

I had the same problem with my install on the EDIS. Had the saw wire in the wrong spot. My 49 year old eyes let me down!

 

Great work Pete!

 

 

Derek

 

Thanks guys.

 

Derek, you've got a couple on me... Oh yea, and your TB setup is at least 3 times better than mine...

 

I checked the signals at the EDIS module and the SAW is changing pulsewidth with advance as it should. The problem I am seeing is only a 2.5V waveform. I thought I checked it at the MSII on the stimulator and it was 5V (as it should be). I am also only seeing around 8V on the PIP (should be 12V). I checked the connections and also the scope probe. I also swapped in my spare module. I'll figure it out next weekend...

 

Pete

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  • 2 weeks later...

Last update until dyno tuning in April. Fixed the EDIS timing issue. Now has nice crisp throttle response after playing with the Megasquirt acceleration enrichment settings.

 

All back together with wiring dressed up. Not the most beautiful engine, but I guess beauty is in the eye of the beholder. It's a road racer, it's going to get dirty.

 

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Thanks Guys,

 

Yes, Fram. OK, they were on sale. I blew a head gasket last year and I'm still running cheap oil and filters through it to get the last of the milk out of it. It IS a budget racer after all. :mrgreen:

 

Yea, I know the red and blue fittings are a bit much, but I had a fuel leak and engine fire last year, so I'm not taking any chances with plain old EFI hose and clamps. The red/blue fittings are a lot cheaper than the black ones for some reason. The thermostat housing my powdercoat guy gave to me, so might as well add even more bling to the engine...

 

Pete

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