R35 GTR v My 944 Turbo
- Thread starter bennyboy
- Start date
DivineE
New member
No idea what boost I hit and it's hard to compare to more recent experiences but when my totally standard K26/6 car got a stuck wastegate (my fault) the car was VICIOUS. I loved it. It can't have produced more than 300hp but for each 2sec burst before you had to back of the throttle to avoid the overboost kicking in, it felt as violent as anything I've ever driven.
It's the acelerating rate of acceleration I love in high boost turbo's. Feels amazing.
It's the acelerating rate of acceleration I love in high boost turbo's. Feels amazing.
It's not too difficult to build a car to take higher boost. I don't think you guys have access to E85 though yet?? That is the wonder juice. I ran my car regularly on 1.5bar and it also hit 2.1 bar a few times when a vacuum line worked loose. Building up the motor to take extra load is doable as well. Bigger headstuds, metal headgaskets, standalones etc...
TTM
Well-known member
This is something I really am not sure of.
We are always limited to what the bores can take in terms of lateral load, so I don't understand how an engine could "take" boost levels such as 1.5 bar without wearing out cylinder bores more quickly than at 1.2 bar.
For sure we can run levels of boost higher than 1.2 bar and still avoid knock with high octane fuels such as E85 but the bores will still work harder and destroy themselves much more quickly than with boost levels lower than 1.2 bar, well at least when using Alusil bores!
MarkK
Active member
My red turbo has been running 1.5 bar for a few years now,it gets used properly not just for a dyno glory run and i can say it has been incredibly reliable,last year it did two very hard 1200 plus mile trips to the ring and Spa.I reckon tuned properly and regular maintenance these cars are very tough indeed.
944 man
Active member
I couldnt post it at the time, but the original Skyline R32 GT-R cost 5.4 million Yen (how do I get different characters on a Mac?). At the historical exchange rate that means that it cost approaching £45,000. Something to consider for those who were suggesting that it was a cheap car..... Thats a domestic price too btw, to which Ive added CPT and VAT @ 15%: Im sure that itd have been dearer after import cost and duties and concessionaires profits.
DivineE
New member
Has anyone seen a car thats run high boost for an extended period stripped down? I haven't but I would be interested to see what wear, ovaling is present on the bores compared to a standard car at similar mileage?
Tony's turbo has been running pretty high boost for a long time (certainly more than standard) and thats probably got 190k on it by now? I wonder at what point the acceleration of wear starts to become significant? I would be very happy if a car did 100,000miles between rebuilds. How many people have ever done 100,000miles in their cars? If you have I'd be willing to bet you'd feel it had justified a rebuild after that time.
Tony's turbo has been running pretty high boost for a long time (certainly more than standard) and thats probably got 190k on it by now? I wonder at what point the acceleration of wear starts to become significant? I would be very happy if a car did 100,000miles between rebuilds. How many people have ever done 100,000miles in their cars? If you have I'd be willing to bet you'd feel it had justified a rebuild after that time.
appletonn
New member
I would have though that, subject to using a top quality fully synth oil and regular oil changes, the better engine protection brought by the modern oils would outweigh the increased loads from the higher boost levels.
The higher boost levels are only 'abusing' the engine for a percentage of the time (ie hooning time
]) so I wouldn't expect significantly accelerated wear rates, as long as the car isn't being abused when cold etc?
The higher boost levels are only 'abusing' the engine for a percentage of the time (ie hooning time![
]) so I wouldn't expect significantly accelerated wear rates, as long as the car isn't being abused when cold etc?
MarkK
Active member
I agree,always warm the car up and i change oil on the red one every 3000 miles or so,and filters and plugs, it gets really pampered,oil consumption is fine,it runs great so far anyway.
If one day it needs to be rebuilt i would keep it in exactly the same state of tune , i would really miss it otherwise.
If one day it needs to be rebuilt i would keep it in exactly the same state of tune , i would really miss it otherwise.
sawood12
New member
The problem with high boost pressures isn't to do with pressure at all, it is more to do with controlling combustion to ensure temps don't get too high and burning is controlled and knock. It is high temps and knock that kills engines, not pressure. Max pressure is achieved at TDC where the volume of the comustion chamber is at its smallest so the cylinder walls don't really come into it, and once the piston is decending the pressure is reduced despite the rapidly expanding post-ignition gasses by the decent of the piston i.e. converting pressure into torque. 944 turbos have run over 1.5 bar before and survived to tell the tale, though I wouldn't expect much longevity at those pressures.
Exactly Thom. There's no real way of avoiding extra load increasing wear. Well, certainly in Alusil bores. With Steel liners you would minimise this dramatically.
My point being that you can run extra boost and hold the motor together for extended periods of time. As you would know, the Jap car guys are running 35psi etc...
Scott I would assume though that with the increase in boost you are increasing heat and load as well as increasing the chance of knock. It's easy to run at 1.5bar especially if you've got the right fuel. Of course the higher load you run the shorter the components will last. Enter at your own risk. [
]
Because the none vertical position of the conrod a sideways force must be exerted by the piston on the bore, this is what wears the bore. They go oval across the block eventually, and the piston skirt wears too.
The more and better lubrication the less the wear will be.
If you put more fuel and air into a cylinder in a given time ALL the forces will be greater, as will the temps, all of which will lead to more wear.
You can reduce the temps and keep knock down by over fueling but too much will affect the lub!.
So you will get increased wear but it should not be excessive.
My gurss is that other parts of a high boost engine will give up before the piston / cylinder if its properly fueled lubbed etc ie valves head gasket etc
Think thats what I mean!
Mike
The more and better lubrication the less the wear will be.
If you put more fuel and air into a cylinder in a given time ALL the forces will be greater, as will the temps, all of which will lead to more wear.
You can reduce the temps and keep knock down by over fueling but too much will affect the lub!.
So you will get increased wear but it should not be excessive.
My gurss is that other parts of a high boost engine will give up before the piston / cylinder if its properly fueled lubbed etc ie valves head gasket etc
Think thats what I mean!
Mike
My engine did Over 70k miles running 18PSI and the bores were perfect (mobil1 15/50 and Silkolene Pro R) however then I had a temp sensor fail and was overfuelling heavily which I did nothing about and destroyed one bore in less than 10K. In fact before I had the head off the first time at circa 170k it was running significantly more boost for very short periods as the boost controller failed, I saw close to 30Psi and wheelspin in 4th very briefly.
I have seen a number of pictures of cracked bores on rennlist one was running water injection and massive boost with a small inefficient turbo (heat). I think the lack of support to the tops of the bores is the weak point in these engines for high boost, I know that there are various ways of resolving this.
I imagine them moving around like the nozzles of a saturn five at high temps and pressures. My feeling is 18PSI is okay with correct mixture and you can get away with 20/21 with lots of work on the ignition and fuel system, however I think any small degradation could cause big issues quickly.
I have no experience of other fuels however which will not behave in the same way.
Detonation (knocking) is the big risk to engine life and higher than normal boost it will destroy the engine in seconds, incorrect fuelling will destroy it in a few thousand miles - the increased wear in normal use with correct running is a minor factor in comparison.
I have seen a number of pictures of cracked bores on rennlist one was running water injection and massive boost with a small inefficient turbo (heat). I think the lack of support to the tops of the bores is the weak point in these engines for high boost, I know that there are various ways of resolving this.
I imagine them moving around like the nozzles of a saturn five at high temps and pressures. My feeling is 18PSI is okay with correct mixture and you can get away with 20/21 with lots of work on the ignition and fuel system, however I think any small degradation could cause big issues quickly.
I have no experience of other fuels however which will not behave in the same way.
Detonation (knocking) is the big risk to engine life and higher than normal boost it will destroy the engine in seconds, incorrect fuelling will destroy it in a few thousand miles - the increased wear in normal use with correct running is a minor factor in comparison.
sawood12
New member
The design of the piston crown and piston rings ensure that forces are shared equally around the circumference of the cylinder walls. If you were getting more force on one side then the engine wouldn't last 2 miles - the hardened silicone layer on alusil bores is only microns thick - thinner than a human hair, and if compromised by 'ovaling' of the cylinder then you'd very quickly compromise that layer and start chewing into the substrait material. The thin hardened layer in alusil bores is pure silicone and is significantly harder than steel/iron therefore doesn't wear at all, which is why you can get away with such a very thin layer with the engine bein capable of over 300k miles in stock form.
The engine canted over at an angle doesn't cause extra wear, in fact it reduces the load on the piston and con-rod pins compared with a vertical configuration. It is not unusual for in-line enignes to be canted over at an angle for this reason. Due to the large diameter of the pistons alot of force is generated at the piston crown (Force = pressure x area) so anything that can be done to reduce the shear forces on the pins is worthwhile.
The engine canted over at an angle doesn't cause extra wear, in fact it reduces the load on the piston and con-rod pins compared with a vertical configuration. It is not unusual for in-line enignes to be canted over at an angle for this reason. Due to the large diameter of the pistons alot of force is generated at the piston crown (Force = pressure x area) so anything that can be done to reduce the shear forces on the pins is worthwhile.
Neil Haughey
New member
I thought the crank was inline with the cylinder bore in a 944? It has to be offset to reduce wrist pin stress, as Honda did on their 2.2 diesel. Engines are canted over for lower CofG and better packaging.
Posts made and opinions expressed are those of the individual forum members
Use of the Forum is subject to the Terms and Conditions
