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  #1  
Old 07-30-2009, 04:49 PM
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Turbo question

This one is only semi-Mercedes related...

I recently bought a low-mileage good running GM 4.3 L V6 diesel engine out of a FWD 84 Olds Cutlass for a couple of hundred bucks. THIS IS NOT one of the converted gasser V8s that GM had such disastrous problems with. It has 14 head bolts per head and is built appropriately beefy for a diesel. Almost all reports are that this is a very good motor, but it was just introduced at the wrong time - right after several years of the GM V8 diesels being out there on the road and failing miserably. By the time the V6 was engineered, produced, and introduced, the public had such a bad taste in their mouth for the GM diesels that nobody wanted one and the 4.3 L was discontinued after only 3 years.

Anyway, this particular motor mates up to the same trannies as the GM 2.8 L V6 gassers. It just so happens that at about that same time, Jeep introduced the Cherokee - and the first ones on the market had either the GM 2.8 L V6 gasser (putting out 115 HP and 150 ft-lbs torque), OR a 2.1 L Renault turbo diesel (producing 85 HP and 132 ft-lbs torque). Both of these engines mated up to the same AX5 5-speed manual, and the 2.8 L was also offered with the A904 automatic. For some reason they never offered the automatic behind the diesel - even though it would obviously handle anything the little Renault mill could dish out.

Well, enough history - fast forward to the present day. I recently made another aquisition - a 1986 Jeep Cherokee with an A904 automatic tranny and a 2.8 L V6 that has one rod sticking out the side of the block (!) for the princely sum of $100. So now you can see where I'm going with this. I'm getting ready to transplant the 4.3 diesel into the Cherokee. It should almost drop right in with very little trouble.

In stock trim the 4.3 only makes 85 HP - the same as the Renault turbo diesel - but it pumps out a respectable 165 ft-lbs torque - more than either the 2.1 L turbo diesel OR the 2.8 L gasser. Here's where the story takes a turn towards the Mercedes marquee - and where I start asking questions...

I have a spare turbo setup from an OM617 and I'd like to graft it onto the 4.3 L V6. Since it was installed in a FWD car, GM, in their infinte engineering wisdom decided not to run dual exhausts. Instead they chose to make the 2" downpipe from one exhaust manifold cross under the engine, connect to the other exhaust manifold, and then all of the exhaust from both banks exits that manifold through a larger 2.5" pipe. It is almost as if they planned to add a turbo to this engine right from the start.

Here are my thoughts, and I'm hoping the turbo gurus around here can either tell me I'm on the right track, or tell me where I'm going wrong. On the 3.0 L OM617, the stock turbo maxes out at around 14-15 PSI. So if it were on a 4.3 L (based on the volume of air being taken in), with roughly 1.4 times the displacement, the turbo compressor ought to be able to supply enough volume to make about 2/3 that much pressure - something like 9 or 10 PSI max. Conversely, since the volume of exhaust gasses being pushed out through the turbo impeller is 1.4 times greater, the turbo should also get enough flow to start to spool up at about 70% of the RPMs that it takes to spool it on the 3.0 L (the inverse of 1.4 = .71 or 71%). Assuming it works that way, the turbo would start to spool below 800 RPMs - almost at idle, and would spool up to its wastegated max pressure really quick.

I'm thinking that if the wastegate can be adjusted to limit boost pressure to around 7-10 PSI, then dumping the excess exhaust through the wastegate will also keep the turbo from being too big of a restriction on the exhaust flow (creating excessive backpressure) and keep the turbo from over-speeding.

My goal here is to bump the HP output of the 4.3 L to at least the same HP output as the 2.8 L gasser, and of course the torque would increase proportionally. If I can get it up to 115, maybe even a little higher (130HP and 250 ft-lbs torque would be AWESOME!) I'd be one happy camper. I figure that if by adding a turbo Renault could get the same HP out of the little 2.1 L diesel (with half the displacement) as what GM got out of the NA 4.3 L, then it doesn't seem unreasonable to expect that adding a mild turbo boost (and turning up the fuel delivery of course) on the 4.3 L ought to be able to bump up its output something like 40%-50%. If it works out that way, this ought to be a really cool project.

Trouble is, I'm not that well versed in turbos, so I'm not sure it will all work this way. It seems logical, but I just don't know for sure, so...
CALLING ALL turbo gurus! Please let me know what you think about the idea and my thought processes here...

__________________
1984 300 Coupe TurboDiesel
Silver blue paint over navy blue interior
2nd owner & 2nd engine in an otherwise
99% original unmolested car
~210k miles on the clock

1986 Ford F250 4x4 Supercab
Charcoal & blue two tone paint over burgundy interior
Banks turbo, DRW, ZF-5 & SMF conversion
152k on the clock - actual mileage unknown

Last edited by rcounts; 07-30-2009 at 05:25 PM.
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  #2  
Old 07-30-2009, 05:57 PM
Simpler=Better's Avatar
Ham Shanker
 
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Location: Baltimore, MD
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Assuming your injection pump can keep up, this should work.
You will need to verify that the oil pump in the GM is adequate-I've heard that all GM oil pumps are crap. YMMV
Install an oil cooler, and do your plumbing so that the turbo gets the coldest fresh-filtered oil possible.
Install an adequately-sized intercooler, so that you can keep your exhaust temperatures down.
Install a boost gauge, pre-turbo exhaust pressure gauge, and pre-turbo exhaust gas temperature gauge.

Hang on tight!
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  #3  
Old 07-30-2009, 06:08 PM
Banned
 
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Hi, I have never heard of the 4.3 gm diesel v6. the exhaust roughting you mentioned is just like a martins turbo systems 350 chevy draw thru setup I had-i still got the exhaust part, sold the intake. a v6 diesel probably wont have the life of a inline engine, but -you got it setting around so what the hey!
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  #4  
Old 07-30-2009, 07:43 PM
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Quote:
Originally Posted by Simpler=Better View Post
Assuming your injection pump can keep up, this should work.
If it won't there's always propane injection
Quote:
Originally Posted by Simpler=Better View Post
You will need to verify that the oil pump in the GM is adequate-I've heard that all GM oil pumps are crap. YMMV
Good thought - I'll look into that
Quote:
Originally Posted by Simpler=Better View Post
Install an oil cooler, and do your plumbing so that the turbo gets the coldest fresh-filtered oil possible.
Also good thoughts. I was planning on the oil cooler, AND a tranny cooler, but plumbing the cooled oil to the turbo bearings first was something I hadn't considered.
Quote:
Originally Posted by Simpler=Better View Post
Install an adequately-sized intercooler, so that you can keep your exhaust temperatures down.
Think that will actually be necessary with such mild boost pressures and modest fuel supply?
Quote:
Originally Posted by Simpler=Better View Post
Install a boost gauge, pre-turbo exhaust pressure gauge, and pre-turbo exhaust gas temperature gauge.
Hadn't considered a pre-turbo exhaust pressure gauge. I can see what it would do (measure backpressure) but what I can't quite see is why? Watch it to avoid possibly blowing exhaust gaskets? What is the bottom line benefit? Boost and EGT are a given
Quote:
Originally Posted by Simpler=Better View Post
Hang on tight!
Ya' really think it'll be that hot? I'm just looking to get OM617-level HP numbers and maybe a bit more than OM617-level torque out of it. Since the Jeep weighs about the same as a W123, I'm not expecting it to be a rocket
__________________
1984 300 Coupe TurboDiesel
Silver blue paint over navy blue interior
2nd owner & 2nd engine in an otherwise
99% original unmolested car
~210k miles on the clock

1986 Ford F250 4x4 Supercab
Charcoal & blue two tone paint over burgundy interior
Banks turbo, DRW, ZF-5 & SMF conversion
152k on the clock - actual mileage unknown
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  #5  
Old 07-30-2009, 07:51 PM
rcounts's Avatar
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Quote:
Originally Posted by panZZer View Post
Hi, I have never heard of the 4.3 gm diesel v6.
Don't feel like you're the only one pard. A LOT of people have never heard of them. Like I said, the only made them for a couple of years. They actually made two different versions though. The FWD versions that have the same bellhousing pattern as the 2.8 L V6, and the RWD version that has the same bellhousing pattern as the Chevy 350.
Quote:
Originally Posted by panZZer View Post
the exhaust roughting you mentioned is just like a martins turbo systems 350 chevy draw thru setup I had-i still got the exhaust part, sold the intake.
Yeah, the exhaust setups for several aftermarket turbo setups for the Ford IDIs (like the one in my sig) work the same way. That's what makes me think somebody at GM was thinking turbo when they designed the exhaust setup on the 4.3 L
Quote:
Originally Posted by panZZer View Post
a v6 diesel probably wont have the life of a inline engine, but -you got it setting around so what the hey!
Well, its starting with just under 100k, so even if it runs another 75k-100k I'll be happy. I have a line on another one with about the same miles on it that I can get for free - I just have to make a 600 mile round trip to go get it...
__________________
1984 300 Coupe TurboDiesel
Silver blue paint over navy blue interior
2nd owner & 2nd engine in an otherwise
99% original unmolested car
~210k miles on the clock

1986 Ford F250 4x4 Supercab
Charcoal & blue two tone paint over burgundy interior
Banks turbo, DRW, ZF-5 & SMF conversion
152k on the clock - actual mileage unknown
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  #6  
Old 07-30-2009, 09:26 PM
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I use the exhaust pressure to compare it with the intake pressure, but then again I'm running a VNT that has the potential to choke the engine-During calibration I had it set too tight and I couldn't get past 2000rpm; I was pushing 35intake/80exhaust; she was NOT happy. It's probably not necessary with a spring loaded wastegate that will regulate itself.
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$60 OM617 Blank Exhaust Flanges
$110 OM606 Blank Exhaust Flanges
No merc at the moment
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  #7  
Old 07-30-2009, 10:16 PM
ForcedInduction
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Quote:
Originally Posted by rcounts View Post
THIS IS NOT one of the converted gasser V8s that GM had such disastrous problems with.
GM never converted a g@sser.
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  #8  
Old 07-30-2009, 10:23 PM
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Quote:
Originally Posted by ForcedInduction View Post
GM never converted a g@sser.
most of us know that but some people still think so, and still think John Delorean is sitting in prison because he sold cocaine to fund his candadian built, Ford powered, kit car company.
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  #9  
Old 07-30-2009, 10:40 PM
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Originally Posted by TheDon View Post
most of us know that but some people still think so, and still think John Delorean is sitting in prison because he sold cocaine to fund his candadian built, Ford powered, kit car company.
I've spent a fair amount of time on the Olds diesel web sites, so I know they didn't, but as you have pointed out, it is the common belief.

What they did do was engineer a 350 CID diesel block with bore, stroke, exterior dimensions, bellhousing patterns, etc. to allow a lot of parts from both the 350 CID diesel and gasser blocks to interchange. As I understand it, rings, pistons, rods, cranks, bearing, heads, cams, gaskets, etc. can be taken from one block and dropped directly into the other. Where the effort really went wrong was in making the heads interchangeable. Not the same, but interchangeable. That meant that the diesel didn't have enough head bolts to handle the compression - because it had the same number, placement, and size of head bolts as the gasser. The degree of parts interchange is what has lead to the misconception that the diesel block was derived from the gasser.

Every time you mention the GM diesels people always refer to them as being derived from the gasser, which a minority of people know is not true, but it is still the common perception. I made that reference to head off that un-helpful discussion in this thread, and to make the point that the 4.3 L is a different animal than the V8 altogether.

Now that we've pretty well discussed that aspect of GM diesels, is there anything else you or Forced Induction would like to add? I know you both have some knowledge you could contribute on this subject - if you choose to...

BTW, IIRC Delorean went to jail for tax evasion and defrauding investors, didn't he?
__________________
1984 300 Coupe TurboDiesel
Silver blue paint over navy blue interior
2nd owner & 2nd engine in an otherwise
99% original unmolested car
~210k miles on the clock

1986 Ford F250 4x4 Supercab
Charcoal & blue two tone paint over burgundy interior
Banks turbo, DRW, ZF-5 & SMF conversion
152k on the clock - actual mileage unknown

Last edited by rcounts; 07-30-2009 at 11:25 PM.
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  #10  
Old 07-30-2009, 10:57 PM
ForcedInduction
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Now that we've all got that out of our system, is there anything else you or Forced Induction would like to add?
I'd rather put that V6 in a Fiero.
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  #11  
Old 07-30-2009, 11:01 PM
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I've already seen that conversion too Lance. Pretty cool - especially given how much lighter the Fiero is. But a 2-door mid-engined sports car just isn't my style - or at least doesn't suit my lifestyle - as much or as well as the Jeep.

C'mon Lance, I'm giving you the chance to share your knowledge of turbos here - a subject we all know is near and dear to your heart. Why would you want to direct the thread down a rabbit-trail instead? Think the T-3 will be up to the job of providing mild boost on an engine with 1.4 times the displacement of the OM617?
__________________
1984 300 Coupe TurboDiesel
Silver blue paint over navy blue interior
2nd owner & 2nd engine in an otherwise
99% original unmolested car
~210k miles on the clock

1986 Ford F250 4x4 Supercab
Charcoal & blue two tone paint over burgundy interior
Banks turbo, DRW, ZF-5 & SMF conversion
152k on the clock - actual mileage unknown
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  #12  
Old 07-31-2009, 05:15 AM
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R, do you know the peak HP RPM for the 4.3? Also, do you have any idea where to find a map for the T3 on the 617?

Is that 4.3 a 60 deg. or 90 deg. V6?
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Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250
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  #13  
Old 07-31-2009, 11:50 AM
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Originally Posted by KarTek View Post
R, do you know the peak HP RPM for the 4.3? Also, do you have any idea where to find a map for the T3 on the 617?

Is that 4.3 a 60 deg. or 90 deg. V6?
Not sure on peak RPMs, but the HP ratings are given at 3600 RPMs - which I would expect to be at or near the top of the safe operating range since it is a V engine. My V8 IDI Ford redlines at around 3800-4000, but it is governed to top out at around 3400-3600 RPMs.

I've seen the T3 map posted on here somewhere before.

The 4.3L is a 90* V6.
__________________
1984 300 Coupe TurboDiesel
Silver blue paint over navy blue interior
2nd owner & 2nd engine in an otherwise
99% original unmolested car
~210k miles on the clock

1986 Ford F250 4x4 Supercab
Charcoal & blue two tone paint over burgundy interior
Banks turbo, DRW, ZF-5 & SMF conversion
152k on the clock - actual mileage unknown

Last edited by rcounts; 07-31-2009 at 01:50 PM.
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  #14  
Old 07-31-2009, 01:29 PM
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Well, since ForcedInduction hasn't picked my plan apart (yet) I guess the ideas and logic must be pretty sound. If anybody could point out the flaws in it I'm sure he could - and would.

I'm really getting excited about this. I'll be going to picking up the engine at my buddy's garage and towing the Jeep home on Saturday. If anyone is interested I'll start a thread about the build and keep it updated.
__________________
1984 300 Coupe TurboDiesel
Silver blue paint over navy blue interior
2nd owner & 2nd engine in an otherwise
99% original unmolested car
~210k miles on the clock

1986 Ford F250 4x4 Supercab
Charcoal & blue two tone paint over burgundy interior
Banks turbo, DRW, ZF-5 & SMF conversion
152k on the clock - actual mileage unknown

Last edited by rcounts; 07-31-2009 at 01:49 PM.
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  #15  
Old 07-31-2009, 04:05 PM
KarTek's Avatar
<- Ryuko of Kill La Kill
 
Join Date: Jun 2007
Location: Bahama/Eno Twp, NC
Posts: 3,258
You seem to think through your plans pretty well. In theory I think that since the turbo supports 125 or so HP on the Benz, it should support it on the 4.3. When I get back to the office on Monday, I'll try to plug in some numbers into my turbo calculating spreadsheet.

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250
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