Boost, head gaskets and bmep
03-27-2004, 12:15 AM
#17
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Marc,
My car went 20 years and 30,000+ miles on the original stock head gaskets. They were seaping coolant into the valley, but this had nothing to do with the turbocharging, they simply rotted. The original gaskets (still have them) were Reinz wide fire ring gaskets. I could run the car on 87 octane with 8 lbs of boost, no issue but I had a lot of fuel in it so i am sure that played a role.
When I upgraded I looked long and hard for some wide fire gaskets, but they simply were not available in 95 mm and I wanted my project done, so I am on the stock narrow fire ring Reinz gaskets with 12-14 lbs of boost and I run 93 octane. No problems thus far and I have put 7,500 miles on the car since last year.
I run 24 lbs of boost in my Audi with no head or special gasket work, but that was designed as a boosted motor so it is not a fair comparison.
My car went 20 years and 30,000+ miles on the original stock head gaskets. They were seaping coolant into the valley, but this had nothing to do with the turbocharging, they simply rotted. The original gaskets (still have them) were Reinz wide fire ring gaskets. I could run the car on 87 octane with 8 lbs of boost, no issue but I had a lot of fuel in it so i am sure that played a role.
When I upgraded I looked long and hard for some wide fire gaskets, but they simply were not available in 95 mm and I wanted my project done, so I am on the stock narrow fire ring Reinz gaskets with 12-14 lbs of boost and I run 93 octane. No problems thus far and I have put 7,500 miles on the car since last year.
I run 24 lbs of boost in my Audi with no head or special gasket work, but that was designed as a boosted motor so it is not a fair comparison.
03-27-2004, 01:11 AM
#19
Burning Brakes
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Jim,
Don't worry about the 'stangs, fear the Cavalier (now THAT's a scary thought) - stinkin' little Ecotec 4 banger is well over 1000 HP with production block, heads, girdle, and drive chain. The rest is/will be catalog GM stuff, other than the blower. Ugh.
Marc,
Do you really feal that there are enough torsional loading (or some other) differences in the 928 block v. the 951 block to have a significant statistical effect on the head gasket longetivity? I'm curious, because I've always found the 951 guys have done this legwork, and most converts nicely when multiplied by 2 . What's the concern?
Greg
Don't worry about the 'stangs, fear the Cavalier (now THAT's a scary thought) - stinkin' little Ecotec 4 banger is well over 1000 HP with production block, heads, girdle, and drive chain. The rest is/will be catalog GM stuff, other than the blower. Ugh.
Marc,
Do you really feal that there are enough torsional loading (or some other) differences in the 928 block v. the 951 block to have a significant statistical effect on the head gasket longetivity? I'm curious, because I've always found the 951 guys have done this legwork, and most converts nicely when multiplied by 2 . What's the concern?
Greg
03-27-2004, 09:57 AM
#20
Marc,
This isn't 928 data but the old Buick V6's could run .5 bar boost all day without an intercooler. They used stock head gaskets and compression ratios. My 931 has been modified to run 1 bar boost with no intercooler and stock head gasket but with this setup I am definitely on borrowed time.
Dennis
This isn't 928 data but the old Buick V6's could run .5 bar boost all day without an intercooler. They used stock head gaskets and compression ratios. My 931 has been modified to run 1 bar boost with no intercooler and stock head gasket but with this setup I am definitely on borrowed time.
Dennis
03-27-2004, 10:34 AM
#21
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Charge cooling and CR is a huge factor ib this equation....
I think spending a lot of money on head gaskets is the cure to the wrong problem.
A guy I work with has a 93 cobra that ran 10 lbs of boost with o-ring head gaskets, no intercooler. It detonated badly and smashed off a couple of ring lands. He now has a stronger bottom end, but I saying he should have a charge cooler for sure.
I guess my point being, if you overly strengthen the head gasket, it may move the point of failure to the next component, which is the piston.
I think spending a lot of money on head gaskets is the cure to the wrong problem.
A guy I work with has a 93 cobra that ran 10 lbs of boost with o-ring head gaskets, no intercooler. It detonated badly and smashed off a couple of ring lands. He now has a stronger bottom end, but I saying he should have a charge cooler for sure.
I guess my point being, if you overly strengthen the head gasket, it may move the point of failure to the next component, which is the piston.
03-27-2004, 04:26 PM
#22
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Marc
thinking about this a little more
As a straight engineering question (and judging by the relative lack of responses) Talk to the guys with 944 Turbos.
The Head gasket on one bank of a 928 motor does not know that it is one of a pair. As far as it knows it is the head gasket on a 2.5 944 Motor. The heads are similar in the way that they meet the block (I know the 2.5 Turbo is an 8 valve) and the top end of the block where it meets the gasket must be similar ?
Or even better blown 968 motors ?
Jon
Black SE
thinking about this a little more
As a straight engineering question (and judging by the relative lack of responses) Talk to the guys with 944 Turbos.
The Head gasket on one bank of a 928 motor does not know that it is one of a pair. As far as it knows it is the head gasket on a 2.5 944 Motor. The heads are similar in the way that they meet the block (I know the 2.5 Turbo is an 8 valve) and the top end of the block where it meets the gasket must be similar ?
Or even better blown 968 motors ?
Jon
Black SE
03-27-2004, 10:07 PM
#23
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I am trying to understand why stock engines being boosted to 8-12 lbs manifold pressure do not suffer significant headgasket failures, regardless of new or old gaskets and I want to know if anyone has any of the following data
I guess my question is why would you expect them to fail in a "significant" manner in the first place.?
Especially on a new gasket, on a head, while not exactly the same, pretty similar to that of the 951. IMHO, 8lbs is nothing on a well prepped motor, which a stock 928 is. (preaching to the choir leader here I suppose)
Its tough when you cant find answers and gather the info you need. Perhaps you will just have to join the rest of us in the SC club, search the internet, read various forums and find out on the "journey"as many of have done and are doing. Collecting our own data and knowledge as we progress/regress. Youve done it with Strokers so this shouldnt be any thing too diffferent.
Added:
https://rennlist.com/forums/showthre...hreadid=123352
Last edited by Tony; 03-28-2004 at 01:13 AM.
03-27-2004, 11:14 PM
#24
Originally posted by jon928se
Marc
thinking about this a little more
As a straight engineering question (and judging by the relative lack of responses) Talk to the guys with 944 Turbos.
The Head gasket on one bank of a 928 motor does not know that it is one of a pair. As far as it knows it is the head gasket on a 2.5 944 Motor. The heads are similar in the way that they meet the block (I know the 2.5 Turbo is an 8 valve) and the top end of the block where it meets the gasket must be similar ?
Or even better blown 968 motors ?
Jon
Black SE
Marc
thinking about this a little more
As a straight engineering question (and judging by the relative lack of responses) Talk to the guys with 944 Turbos.
The Head gasket on one bank of a 928 motor does not know that it is one of a pair. As far as it knows it is the head gasket on a 2.5 944 Motor. The heads are similar in the way that they meet the block (I know the 2.5 Turbo is an 8 valve) and the top end of the block where it meets the gasket must be similar ?
Or even better blown 968 motors ?
Jon
Black SE
Many 968s with boost of some sort. They get the cometic gaskets, lower the compression JUST a bit, and run regular boost of 15-20psi. Not many yet, but more being built.
Whats the compression of the 951? 8 to 1? 8.5? They blow heads all the time - due to detonation due to fueling issues.
03-28-2004, 04:52 PM
#26
Drifting
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Originally posted by Jim bailey - 928 International
B C ..."Yep..." Wow, BC I never ever thought you would be at a loss for words .......
B C ..."Yep..." Wow, BC I never ever thought you would be at a loss for words .......
Just that what you say is true.
Most 928 people tuners won't admit it though.
They think they are king of the hill, with whatever they built.
It's true in most hot-rodding circles.
Imports especially.
All talk about how fast they are, but it is actually
not that fast compard to American "hot rods".
If you want to tout reliability, keep it stock.
If you want to start pounding your chest about speed, power, etc,
you have to be willing to compare to those other speed freaks out there...
03-28-2004, 09:28 PM
#27
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I am trying to sort out the BS from facts and am looking for data. To those who posted, thanks...it is a good start!
Tony, I have already researched this topic, and am now looking for verification from the existing SC crowd.
How many of the current group of SC 928 have blown head gaskets, at what level of boost, how long did the gakets last, were they new or old, what octane was used, how many miles, etc.?....we need more data. The truth is out there...right?
I have looked at the 944T data...but they begin with significantly lower compressions and have excellent intercoolers.....I use their BMEP both factory and stock and have some estimates on relaibility based on BMEPS that I want to compare to SC boosted 928s and see if they are the same or similar.
Marc
DEVEK
Tony, I have already researched this topic, and am now looking for verification from the existing SC crowd.
How many of the current group of SC 928 have blown head gaskets, at what level of boost, how long did the gakets last, were they new or old, what octane was used, how many miles, etc.?....we need more data. The truth is out there...right?
I have looked at the 944T data...but they begin with significantly lower compressions and have excellent intercoolers.....I use their BMEP both factory and stock and have some estimates on relaibility based on BMEPS that I want to compare to SC boosted 928s and see if they are the same or similar.
Marc
DEVEK
03-28-2004, 09:34 PM
#28
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Jon,
There are many differences between a 944 and 928 engine....for example, a 928 does not have twice the cooling capacity of a 944, nor is the firing order the same, or the head studs location to c the same, or for that matter, the CR, piston materials (turbo only), in some cases the rods are different, the boost curves are also very different....for a given rpm range, or pull, a SC 928 will have more cumlative time under boost than a Turbo engine, stock turbos 944 go to .8 bar for x seconds then drop off to lower boost levels, fuel delivery is temp compensated, etc...the list is endless!
Lots of differences!
Marc
DEVEK
There are many differences between a 944 and 928 engine....for example, a 928 does not have twice the cooling capacity of a 944, nor is the firing order the same, or the head studs location to c the same, or for that matter, the CR, piston materials (turbo only), in some cases the rods are different, the boost curves are also very different....for a given rpm range, or pull, a SC 928 will have more cumlative time under boost than a Turbo engine, stock turbos 944 go to .8 bar for x seconds then drop off to lower boost levels, fuel delivery is temp compensated, etc...the list is endless!
Lots of differences!
Marc
DEVEK
03-28-2004, 09:55 PM
#29
Drifting
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Here is the info on my car.
120k mi stock head gasket (as far as I know). When I got the car 10k mi ago it had a failed radiator due to corosion. I would expect the same condition to effect the head gasket.
I have not had a head gasket failure
~4kmi last summer, 4.5 psi, Jag/Eaton M112, non intercooled, 91 octane
~3.5kmi ~Oct 03 to date, 7 to 8.8 psi, Whipple twin-screw 2300AX, very small IC, 91 octane. 15 quarter mile runs almost back to back one night at 8.8psi. POC DE and short track event at 8.8 psi. May I add, all on a 6 rib belt. Actually the POC event was run on a 5 rib as I shreaded the last rib off when I made a faulty tension in the dark.
HTH,
Andy K
120k mi stock head gasket (as far as I know). When I got the car 10k mi ago it had a failed radiator due to corosion. I would expect the same condition to effect the head gasket.
I have not had a head gasket failure
~4kmi last summer, 4.5 psi, Jag/Eaton M112, non intercooled, 91 octane
~3.5kmi ~Oct 03 to date, 7 to 8.8 psi, Whipple twin-screw 2300AX, very small IC, 91 octane. 15 quarter mile runs almost back to back one night at 8.8psi. POC DE and short track event at 8.8 psi. May I add, all on a 6 rib belt. Actually the POC event was run on a 5 rib as I shreaded the last rib off when I made a faulty tension in the dark.
HTH,
Andy K
03-29-2004, 01:23 PM
#30
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Yes, CR is differnt on the S4 and all 4 valve 928s for sure. Combustion chambers on the 4.5 are similar to the 944 and the cr is lower for sure, that is why I am starting with a 1980 4.5 car, becasue I know the CR isn't going to kill the engine when I add boost.. No doubt the mapping of the motronic takes all of this into account.