Thread: Super MPGuino?
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Old 02-14-2010, 03:19 PM   #29 (permalink)
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Originally Posted by bobski View Post
I'm not sure about the '88-91 Prelude since it's sort of a... umm... ******* child of the B-series engine family, but many times the electronic VSS (vehicle speed sensor) units found installed on the transmissions of newer vehicles are drop-in replacements for the cable drive gear found in older cars.
The 88-91' Preludes are weird. In between '89 and 90' Honda made a lot of changes to the Preludes on the internals, and some body modifications. The 89' Preludes and prior have mechanical speedometers with a small voltage generator just before the actual part that moves your speedo *which is what fails on a lot of preludes*, and the 90' Preludes have electronic speedos that have the generator in the transmission. Other slight variations like engine type, and what patterns they put at the end of the turn signal/wiper assembly, but most don't really apply.

I'm also not planning on swapping out the VSS unit on my trans. It runs a cable, which is running just fine, and it turns my odometer. Although the ability to have an electronic trip function would be rather nice, I probably won't consider getting parts for such a swap until it comes time for me to pull my transmission out and swap it in.

It is possible to do the conversion on a 89' Prelude to an electronic VSS, but then you'd have to probably do some cluster internal swapping, and things just get sticker from there if you plan on keeping stock cluster settings anyways.

It might be tempting to design an entirely new cluster based with the super-mpguino as its core. More things to fail yes, but that way it could be done perfectly. Only problem for me is that I really like the stock look in these cars, and it would be pretty hard to make it look completely stock.

For coolant temperature, there should actually be two pickups. A single-wire sender for the gauge, and a two-wire sensor for the ECU.
Yep. Well, I can't say that there are only two pickups, because mine might have three if that's the case. It has one single wire sender all right, but it also has two double wire senders right next to it. One of those lost connection and I now have custom splices into it, but it's still not working, which could provide the part of it being the ECU sensor, but they are just smack next to each other. Less than 2" away, on the same piece of coolant pipe so to speak. If they are just single wire senders, I might have to attack mine with a soldering iron, as my temp gauge is flat-lining until it is almost at highest temp. It only started after I messed with the dual wire sensor, but since the single wire send is next to the dual, it could have been damaged as well.

That means the '89 Prelude should have a pulse-driven tach. The ignition control module in the distributor generates a signal pulse every time it fires the ignition coil -- twice per crankshaft rotation.
And after another check under the hood, right again. I looked at the cruise control cable insert and never bothered to follow it. But yeah, there are two pairs of wires that come off the coil and go straight to the harness. So then electronic tachs are possible, and probably fairly easy.

Try to find a decent Honda/Prelude enthusiast forum to find more info. - Powered by vBulletin. Massive website, awesome people, and lots of knowledge. I'm over there as well, same user name.

For the TPS sensor, it could come in handy by using that as a factor when it could come to individual cylinder cutoffs. How much further the throttle has to be increased when you have say 2/4 cylinders cut off, how much this effects mpg, etc.

I think the whole MAP sensor got explained to me once before, but it didn't stick long, because I forgot what that thing does again. If somebody wants to refresh my memory on it, that would be awesome.

bobski - You mentioned you had a CRX, but have you ever done any work with Preludes? You sound like you know Honda's in general pretty well.
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1969 VW Bug - Daily Driver
1975 VW Baja - Current Project
1989 Honda Prelude Si 4WS (RIP)
1995 Honda Prelude Si (Traded)
1980 Fiat Spider 2000 (Sold)
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