1986 951 Too Much Boost?
03-06-2021, 09:09 PM
#16
Three Wheelin'
Meandering along on this mystery, I took apart the manual boost controller to clean it out and bench tested to make sure it was working ok.
Put it back in the car with a boost gauge on the output side of the boost controller and verified only 2-4 libs of pressure when I set it at minimum (that goes to the secondary port on the dp wastegate).
Even still, I was still getting too much boost in 2nd gear, so I opened up the DME. There was a handwritten note on the mylar sheet "DME 944T.M89 8.25.95" and a business card for "Club Sport Autowerks Engineering." The chip had what looks like an original sticker (# 1267355235) on it, but after I cleaned the DME metal case, there was a handwritten note like "Stage (unclear) Chip 8/95".
So of course I google "Club Sport Autowerks" and get this article about the guy whose card I found in the DME - 1 month after the date on the DME mylar this happens:
https://www.nytimes.com/1995/09/26/n...olice-say.html
Let me know what this sounds like or if anyone has ever heard of "Club Sport Autowerks".
I assume that the EPROM was reprogrammed but not re-marked.
It would be great to borrow an original chip to see if the boost gets scaled back to reasonable levels.
Next step is to do an isolated pressure test of the wastegate primary port.
Put it back in the car with a boost gauge on the output side of the boost controller and verified only 2-4 libs of pressure when I set it at minimum (that goes to the secondary port on the dp wastegate).
Even still, I was still getting too much boost in 2nd gear, so I opened up the DME. There was a handwritten note on the mylar sheet "DME 944T.M89 8.25.95" and a business card for "Club Sport Autowerks Engineering." The chip had what looks like an original sticker (# 1267355235) on it, but after I cleaned the DME metal case, there was a handwritten note like "Stage (unclear) Chip 8/95".
So of course I google "Club Sport Autowerks" and get this article about the guy whose card I found in the DME - 1 month after the date on the DME mylar this happens:
https://www.nytimes.com/1995/09/26/n...olice-say.html
Let me know what this sounds like or if anyone has ever heard of "Club Sport Autowerks".
I assume that the EPROM was reprogrammed but not re-marked.
It would be great to borrow an original chip to see if the boost gets scaled back to reasonable levels.
Next step is to do an isolated pressure test of the wastegate primary port.
A quick way to eliminate the MBC as the issue and check the wastegate spring setting is to simply disconnect the line from the lower port of the wastegate (as shown in your pic) and plug the open end of the hose that is connected to the MBC . If your boost pressure is now lower, then the "issue" is with the MBC. If it is the same, there might be a problem with your wastegate or boost signal line.
Testing a wastegate means removing the pipe from the outlet side (so you can see the bottom of the wastegate poppet valve), and finding a means of connecting a regulated air pressure source (usually an air compressor with an inline pressure regulator) and see what pressure causes the wastegate valve to lift.
By the way, since your car has a MBC and presumably has the factory cycling valve bypassed, there is no way for a chip in the KLR or DME to influence the boost pressure. This means that there is also no way for there to be overboost protection, so be careful!
Another thing to check for is a restrictor jet in the banjo fitting that connects the wastegate signal hose to the boost pipe, which was an old, crude means of increasing boost.
Last edited by Droops83; 03-06-2021 at 09:38 PM.
03-08-2021, 11:44 AM
#17
Instructor
Thread Starter
Hi Chris - thanks for the suggestions.
Having the MBC shouldn't negate the boost override in the DME / KLR by itself. The KLR is still connected and monitoring boost. I clamped both sides of the MBC and didn't see much of a change. Given that I am not sure exactly what chip I have, it's quite possible that the DME no longer has the overboost protection code.
Also - running the primary port of the wastegate open will get no blow off at all, so I'll still be at the high boost.
But I will try setting the primary at 15-20 lbs or so using my motive to see if I can get the wastegate to open while driving. If there's no difference, then I assume the wastegate is stuck closed.
Having the MBC shouldn't negate the boost override in the DME / KLR by itself. The KLR is still connected and monitoring boost. I clamped both sides of the MBC and didn't see much of a change. Given that I am not sure exactly what chip I have, it's quite possible that the DME no longer has the overboost protection code.
Also - running the primary port of the wastegate open will get no blow off at all, so I'll still be at the high boost.
But I will try setting the primary at 15-20 lbs or so using my motive to see if I can get the wastegate to open while driving. If there's no difference, then I assume the wastegate is stuck closed.
03-08-2021, 11:16 PM
#18
Three Wheelin'
Hi Chris - thanks for the suggestions.
Having the MBC shouldn't negate the boost override in the DME / KLR by itself. The KLR is still connected and monitoring boost. I clamped both sides of the MBC and didn't see much of a change. Given that I am not sure exactly what chip I have, it's quite possible that the DME no longer has the overboost protection code.
Also - running the primary port of the wastegate open will get no blow off at all, so I'll still be at the high boost.
But I will try setting the primary at 15-20 lbs or so using my motive to see if I can get the wastegate to open while driving. If there's no difference, then I assume the wastegate is stuck closed.
Having the MBC shouldn't negate the boost override in the DME / KLR by itself. The KLR is still connected and monitoring boost. I clamped both sides of the MBC and didn't see much of a change. Given that I am not sure exactly what chip I have, it's quite possible that the DME no longer has the overboost protection code.
Also - running the primary port of the wastegate open will get no blow off at all, so I'll still be at the high boost.
But I will try setting the primary at 15-20 lbs or so using my motive to see if I can get the wastegate to open while driving. If there's no difference, then I assume the wastegate is stuck closed.
Also, when you say wastegate "primary," I'm assuming you mean the main signal hose, which is the upper port on the Lindsey dual-port WG---Tial and most other aftermarket dual-port WGs are the opposite. In my previous post I suggested disconnecting the lower, "secondary" signal line that is used to counteract the main spring pressure (which is what you are regulating with the MBC valve). But since you already drove it with both sides of the MBC hose clamped, that would basically accomplish the same thing.
03-09-2021, 02:49 PM
#19
Vacuum pump
I have a similar setup and had overboost problems it was a vacuum line problem. You can check the opening of the waste gate valve with a hand held vacuum pump. Most boost problems are vacuum or exhaust leaks.
03-11-2021, 01:42 PM
#20
Instructor
Thread Starter
Thanks @RKT951 - any easy means of checking it without pulling off parts to visually inspect? I pumped it up to 20lbs and it held pressure for a reasonable time. That doesn't mean it opened, but at least I know that there's no leak in the the line going to the wastegate.
I'm not seeing vacuum issues (checked vacuum multiple times). An exhaust leak would result in low boost, correct?
I'm not seeing vacuum issues (checked vacuum multiple times). An exhaust leak would result in low boost, correct?
06-24-2021, 12:29 PM
#21
Instructor
Thread Starter
Looks like I've sorted this out - I went back to a stock DME chip and zip tied one of the boost lines going to the DP wastegate (it had fallen off the other day).
I still need to measure the boost more accurately, but the in car gauge is definitely peaking at a lower level - closer to ~1.75 and doesn't pull ing as strong at WOT.
1 mystery down, 950 left.....
I still need to measure the boost more accurately, but the in car gauge is definitely peaking at a lower level - closer to ~1.75 and doesn't pull ing as strong at WOT.
1 mystery down, 950 left.....
01-26-2022, 06:32 PM
#22
Instructor
Thread Starter
A few months later....put in a new digital ProSport boost gauge that tracks peak boost and replaced my MBC (old one was was leaking air through when it was supposed to be fully closed) and we are in a much better place. Max boost fully closed is now 11-12psi.
03-07-2022, 02:49 PM
#23
Instructor
Thread Starter
One other item to mention for future searches on Huntley Turbos - I used one of the internet archive utilities to track down the details of the Huntley Turbocharger, which explains the higher boost that I was originally seeing:
'Cheater' Stage I - We have gotten in so much heat because of these turbos we almost pulled them from production! Despite many protests, arguments, etc. We decided to keep them anyway since that is what our customers want, the customer is always right! These turbos got their name because they are bone stock on the outside but anything but on the inside! Though the initial intent was 'pure' in nature the potential implications of these turbos was very obvious to many racing organizations. The Stage I makes as much as 290 HP at the wheels on a 951! With its bigger compressor wheel, modified turbine and machined housings it spools faster than stock using the #6 hot side. It is 100% bolt on.
'Cheater' Stage I - We have gotten in so much heat because of these turbos we almost pulled them from production! Despite many protests, arguments, etc. We decided to keep them anyway since that is what our customers want, the customer is always right! These turbos got their name because they are bone stock on the outside but anything but on the inside! Though the initial intent was 'pure' in nature the potential implications of these turbos was very obvious to many racing organizations. The Stage I makes as much as 290 HP at the wheels on a 951! With its bigger compressor wheel, modified turbine and machined housings it spools faster than stock using the #6 hot side. It is 100% bolt on.