power in signal out of map. sensor

[jeff1234]

Speaking of 86/87 L/M and referring to power and signal wires for the map sensor, when I measure voltage at the three pin plug which has been disconnected from the map I find 5.03 vdc on the wire coming from pin #1 on the red LM plug and 4.96 vdc on the wire coming from pin #19 on the blue LM plug which is the map output signal which reports voltage changes coming out of the map sensor. It doesn't make electronic sense, as I understand it to already have power on that wire. It looks as though pin # 19 is wrong. Can anyone explain how this can work as it presently is. It must be wrong. Anyone seen this before?

[cordes]

There are three wires going to the map. Power, signal, and ground. Think of it as a voltage divider (that's pretty much what it is). The signal wire is the one that will vary with pressure.

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ETA: Is this with the car running? Without the car running then it should be much less than 5v and I see what you're getting at.

[jeff1234]

Cordes, I have been also working with Todd and we think we have finally found the problem. Todd verified that his cars had the same readings with the plug removed from the map sensor. I had the rudimentary idea that you expressed about the voltage divider. More importantly I sent Todd some pictures of my vacuum hosing and we found two or three things incorrectly assembled. I sent him the pictures because once I settled the voltage question I was able to move on in trouble shooting. The voltage question had been haunting me for quite some time. I had the wastegate solenoid plumbed backwards and the fuel pressure T'ed off on the wastegate line to name a couple. I am looking forward to tomorrow to rectifiy these things and test again. Just imagine, all this time I have been trying to solve the detonation problem and all of the problems it has caused because I didn't ask the right questions. I have high hopes for tomorrow. Thanks for responding and for the help you have given me in the past.
Jeff

[cordes]

No problem. You're going to be at SDAC right?

[jeff1234]

I will be at sugar river raceway and the drag strip. I can't afford the hotel rooms etc. for the main events. I live just northwest of the raceway about 8 miles.

[Vigo]

I sure hope you get it figured out and are able to unequivocally enjoy the car again! I've tried to help the best i knew how in other threads, but as you say, sometimes you dont know the right questions to ask, and i probably didn't know the right ones to ask you! Sounds like you are making good progress now.

[cordes]

I will be at sugar river raceway and the drag strip. I can't afford the hotel rooms etc. for the main events. I live just northwest of the raceway about 8 miles.

I'll see you there!

[jeff1234]

Cordes, I tested the car and it ran as it should, however after about 1.5 miles (10 miles since turbo rebuilt) it puked the turbo. I don't know if it was because of previous backfiring and bucking but I got gobs of smoke and could hear the compressor wheel hitting the cover. I will still see you at SRR and Union Grove.
Jeff

[cordes]

Cordes, I tested the car and it ran as it should, however after about 1.5 miles (10 miles since turbo rebuilt) it puked the turbo. I don't know if it was because of previous backfiring and bucking but I got gobs of smoke and could hear the compressor wheel hitting the cover. I will still see you at SRR and Union Grove.
Jeff

That's a bummer. It would have to be some pretty bad bucking etc. to kill a turbo.

[jeff1234]

Vigo, your help has been appreciated. Part of the problem is not being able to stand by the car and look at it. It never occurred to me I could have things switched around. I don't know what I am doing so the learning curve is long, frustrating and expensive. I still have a dream for this car.
Jeff

[jeff1234]

It only bucked a few times but there had been numerous times where when I put it on the floor the car was fighting itself because the fuel regulator was hosed off the waste gate. I am looking at a T3 60 trim from Himni racing. What do you think. It would be a virtual bolt on and with the hosing sorted out should last now. Would it over spin at 18 psi?
Jeff

[Vigo]

What is the rest of the setup? Depending on how well the rest of the setup flows, a t3 60 trim could be spinning pretty fast to keep up 18 psi going into it.

I cant remember, but didnt you have a thread about turbo choice where i recommended a t04 46trim compressor side?

[cordes]

Isn't it just an exducer size difference between that and the S60 wheel? I know the turbo ford guys push their stock T3 60 trim turbos pretty hard without too many problems. Their cross flow heads do better than ours for the same level of boost so I would think that their shaft speeds would be higher by way of comparison.

[jeff1234]

Yes, that is correct. Last year I had this turbo re builder modify mine for that wheel. I reassembled and didn't torque the comp/wheel nut tight enough so it spun loose first time I floored it which damaged the turbo. I sent it to them and ordered the exact wheel I originally got from ebay. When they got it it was the wrong wheel. They said they didn't want to continue with it so I sent stock parts and they rebuilt it stock. Himni has T3/TO4E turbos but the cover looks much larger. What kind of problems would I encounter fitting this turbo to my L body. I know Cindy has her version but it is $150 more than Himni and it's just another rebuild. I'm pretty tired of those.
jeffjeff

[Vigo]

Have you asked Todd about the turbo selection issue?

Sorry about all the turbo issues. I know the t3 60 trim wheel will work, i just dont know if its lifespan will be seriously affected by running 18 psi on a modded motor. I also dont know if it will ever matter based on how much or little you will drive it or whether other things will go wrong. Most turbos seem to go bad at least in part because other things went wrong, so it's hard to say how long turbos last since they are always at the whim of something else breaking and taking them out too.

[cordes]

Agreed Vigo it's really hard to pin down everything with so many factors. Frankly, reading of these troubles makes me realize that someone else is at the other end of the bell curve turbo durability wise. I get at least 150K out of them generally. That's for stuff I don't hot rod though. I killed a used Garrett which was nice and tight in only a few months while running it at 22PSI while in my youth.

The To4E covers are a lot larger. I made a video about this the other day and will be following it up with the whole installation of it.

[jeff1234]

Vigo, yupp, I have asked Todd about it. He is going to look at Himni site. I ask you guys to get a cross section view also. The T3/TO4E that Himni has is just a few dollars more so if it didn't take severe contortions under the hood to install it I would prefer to have it. My engine compartment is stuffed full on the driver side. That is probably not a surprise to most l body users. Lol jeff

[jeff1234]

Hey all, I found out what happened to my turbo. The turbine wheel sheared off at the sealing ring groove. Dead meat. jeff

[Vigo]

Uh.... WOW!

[cordes]

That's a hummer of a failure, but not unheard of. Rare though. At least you tracked it down.