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Discussion Starter #1
I'm brainstorming here and something caught my attention. If one is using individual throttle bodies, one needs both idle ports and MAP ports (assuming one is going to use MAP control). If the Idle Control Valve is closed when not idling and the MAP signal is not used at idle, can those ports be shared? ie only have one port per throat and have both idle control port and MAP ports on the idle block?

Is it so crazy that it just might work?
 

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as the ports are in hi-flow one moment the air is blowing into them and the next it can be sucking.
I cut new ports inline with the axle of the butterfly for the MAP and keep the idle the way it was. it works not too bad I still had some strange up and downs but it at lest it fits in to the VE map and I could drive it.
 

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Discussion Starter #3
I think the direction of flow is the same. Idle air will flow through the ports into the throats. Then when you open up the throttle, the ICV closes and the suction (negative pressure) in the throats will pull air from the ports into the throats. Air isn't actually flowing; there is just a negative pressure in the ports that the sensor measures. If the ICV actually closes all the way it should work. Also important, if the computer really ignores the MAP signal at idle, it should work. It's the transition that is unknown. Anyone can comment?
 

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The transition from pure TPS load sensing to MAP load sensing would need to be user adjustable and accurate.
I have read numerous times that setting up MAP sensed systems on multiple TB turbo cars like the Skyline GTRs requires the ability to switch between TPS based load measuring for small throttle angles and as or just before the engine comes onto boost, the computer uses the MAP sensor from then until the engine comes off boost.

What system are you planning to use?

I'd personally look at using pure throttle position load sensing in a normally aspirated multi throttle set up and use the MAP sensor as an atmospheric pressure sensor if the computer doesn't have 1 built in.
That's how my uncle's Moto Guzzi's Weber/Marelli system works.
 

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Discussion Starter #5
I haven't decided on the system yet. Something budget minded. Gotech or MS. I haven't read too much about MS, discussions seem to be all over the place and not very concise. I can't seem to get my mind around it, so I might just avoid it altogether. There are some to-the-point discussion on Gotech and they have both TPS and MAP setable to what you want.

I don't quite follow your last sentence. Can you expand?
 

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Mabe or mabe not as budget minded as you're after, but there's also Simple Digital Systems who offer pretty complete kits. (you come up with the induction and they cover pretty much everything else, including sensors, senders, injectors and ignition packs if you wanna buy that along with the basic ECU and harness)

They're aircraft use certified which isn't an easy thing to accomplish.

Boardmember Greg Gordon can offer more current/direct info if you ask as he's a dealer.
 

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I don't quite follow your last sentence. Can you expand?
The factory Weber/Marelli system that were used on the twin TB, V-twin Moto Guzzi's used TPS load sensing but also used a MAP sensor as an input to provide correction for different atmospheric pressure and the ram air effect of motor bike at silly speeds.
 

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Why even use vacuum for your fast idle.
I used an anti diesel solenoid off an old carter carby to flip open the throttle a touch. It worked a treat.
 

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My set up and the stock Toyoda ITB seem to be the other way. At idle it gets a great MAP reading and work well. it is where there is a lot of air flow when the map get bad numbers as the ports start to act like a venturi. so I want to go the other way start out MAP then go to TPS. also this lets you use a idle air control valve.
 

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MS also supports blended maps, so you can use a combination of TPS and MAP readings to figure out your load. Strictly TPS can be a hassle on the street.
 

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Shared MAP and idle ports?

Stefano, in response to your original question, I've concluded that separate idle air and MAP circuits are required. The issue is that as idle air flows through to the engine, it is expanding because of the pressure differential that is drawing it into the engine. A MAP signal drawn from an idle air circuit will be unpredictable and otherwise inconsistent relative to what the ECU program is looking for. My own project involves throttle bodies built up from Spica throttles, custom injector carriers and adaptors so that they bolt in in place of the OE Webers. I'm using MegaSquirt1 Squirt'nSpark Extra hardware and its corresponding software. The system does work, but I've been delayed by vacuum leaks here and there which have to be fixed before any tuning can be done.
 
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