Penguinracer

Hi All,
I'm interested in gaining an insight as to the engine durability of highly tuned (400+ WHP) M44 engines.

Does anyone endurance race ( 6 /12/ 24 hour races) a 400+WHP 951 / 968 (either 8V or 16V) and if so how many miles / hours is it covering between rebuilds?

Has anyone put 50,000, 75.000 or 100,000 miles on a 400+WHP 951/968 without issue?

There are guys on these board tuning these cars for sprint races - but it's the road & endurance racing tuned cars about which I'm keen to hear.

Obviously dry-sumping, sleeving & closing the deck should help with durability - but these don't seem to be the norm.
People seem keener to spend on a 3 litre, 16 valve turbo conversion than dry-sumping and MID-sleeving or deck plating.
Obviously attention to thermal management is a significant issue at these power levels.

Tim

GPA951s

For endurance racing , the turbo is a terrible option…you need to make 2 hours in between fuel stops .. the turbo especially at 400hp would barely make 60 min… dont get me wrong i love turbos and race one myself but not endurance. When i race lucky dog, champ, ect always n/a … theres a reason everyone in sp3 and endurance racing goes 3.0l N/A. I just finished building a endurance car with a 3l na…

Penguinracer

The 924 GTP using the predecessor of the M44, but in 2.5 litre, 16 valve, 420 bhp guise finished 7th overall at Le Mans in '81 with Jurgen Bath & Walter Rohrl.

It was accompanied by a 924 GTR (2 litre, 8 valve, 375 bhp) which came in 11th driven by Andy Rouse & Manfred Schurti.
In the previous year Jurgen Barth & Manfred Schurti brought a 924 GTR (2 litre, 8 valve,375 bhp) home in 6th overall, with the identical cars of Andy Rouse / Tony Dron and Derek Bell / Al Holbert finishing 12th & 13th respectively.
The Rouse / Dron and Bell / Holbert cars experienced exhaust valve issues.

These cars were quite capable - 7th OVERALL at Le Mans for a predecessor of the M44-engined 951 is highly impressive if not quite matching the 6th OVERALL of the 924GTR in '80.

With modern technology I would expect a tuned, 400+bhp 951/968 to have no problems with requisite attention to lubrication, block strength, lubrication and the cooling systems.

Has anyone put 100,000 miles on their 400+ bhp road car?

blade7

Block strength? Porsche updated the block with the introduction of the 2.7 engine.

FrenchToast

A handful of people could probably build such an engine, but other parts of the car will break first.

Porsche supposedly ended up detuning the 968 Turbo RS by about 100hp for LeMans spec.

The "M44" installed in the 944 GTP probably shared little if anything with the production block. Plenty of pictures are out there of the engine.

At a suspension and drivetrain level, the 924 GTR and 944 GTP have more in common with a 935 than with any production based 924 variant. So simply putting a fast engine in the car doesn't mean the rest of it will work for long.

Penguinracer

It would be interesting to hear who's put the highest mileage on a 400+ WHP 951/968 road car - and how it's held up.

Has anyone run a car of this tune in 24 hour races such as Nurburgring Endurance Series (NLS - Nurburgring Langstrecken-Serie or its predecessor the VLM - Veranstaltergemeinschaft Langstreckenpokal Nürburgring) or any other 24 hour races?

333pg333

At this stage Tim are you asking out of plain curiosity or is it your intention to do this with your build? It would be an interesting exercise. You'd find out pretty quickly where the weak points are. But you've asked 2 questions. One is about race cars, the other is about road cars. Very different with very different results.

Penguinracer

I'm interested in both - even though they're very different.

On these boards there has long been a fascination with peak power & torque figures from the M44 motor - but really only in the context of sprint races.

What interests me is a tuned motor which is as durable as the stock original. That is, exquisite engineering going into every system to ensure that the tuned road car
can be run as hard as the stock original item with similar levels of durability & reliability - just as a box-fresh GT3 can be thrashed all day without complaint.

Has anyone aimed for GT3 levels of durability from their road car at the 400+ WHP level?
Has anyone put significant road mileage on a 400+WHP M44 engine?
The tuned endurance race car is an extension of the same question - how far can the M44 be pushed as an endurance race engine and still be reliable.

Tim

blade7

Which version of the M44 engine?

Penguinracer

Any of them in turbocharged form so M44/51(220 bhp turbo), M44/52 (250 bhp turbo), M44/41 (3 litre) or the M44/12 (2.7 litre).

It struck me that using 1981 technology the 2.5 litre 16 valve turbo survived Le Mans at 420 bhp.
With modern lubricants, improved parts, 40 years of aftermarket R&D and better turbo's, ECU's etc - that endurance motor figure will have moved on for both a race car and any
tuned road car which we want to be highly durable and run to a good high mileage.

I often think that the nearest race car tune to a top grade highly tuned road car is something designed for 24 hour endurance events.
They're obviously not the same - but both are designed for durability & reliability rather than peak power output.

blade7

So, you have overlooked arguably the best M44 blocks. The thick wall M44.50 and the M44.43/44.

333pg333

Using the modern GT3 Porsche's ability to drive to the trackday and speed about at max rpms then drive home as an comparison, I think it's possible to build something similar. However when you compare n/a to forced induction it's not quite apples to apples with so much extra underhood heat in our cars. 400whp is a fair target for a car like this. Not too difficult to raise those power levels but keeping everything cool is the challenge. I'd say you definitely want the increased capacity of a circa 3ltr motor. Reducing boost levels by comparison to the 2.5ltr is a no brainer. Keeping the head secure is another task. But with some of the improved studs and gaskets available this can be achieved.

Then, as others have mentioned, there are non engine related components. The drivelines, transmissions etc are old. So they'd need a thorough refresh and improvement in some areas. The hubs/bearings/spindles are a weak link and as others have experienced, so are the arms. So they'd need to be considered if you're trying to build an endurance trackday/racer.

In the end, how big is the budget?

blade7

Considering the 24 hours of LeMans as a yardstick, I think the longest distance raced was around 3300 miles. I expect Porsche used a 16 valve head because it was more efficient, requiring less boost to achieve the target bhp. So realistically the S2/968 head is the ideal choice for an endurance engine today.

Penguinracer

I agree that 16 valves is the optimum.
I didn't go there because of the expense, amount of fabrication involved & being happy to retain my original block - but it definitely allows lower boost pressure for any given power target.
Blade...unlike the U.S - you're aware how little aftermarket / development experience there is with these cars in the UK.

Penguinracer

Where it all gets a little complex is around crank flex with the 3 litre crank, then the impact of crank flex on bearing clearances, harmonics etc.
Probably not an issue at the standard road car rpm limit at modest boost for short periods.

I was advised to keep the original short-stroke crank & not weight relieve it at all - the idea being to maximise crank stiffness, optimise harmonics, reduce piston speed and
have a good rod length to to stroke ratio. Closing the deck & dry-sumping were just logical safeguards as was maximising oil cooling - so 16 valve fabrication on top was
more expense & fabrication than I was up for given that I'd done all I could to optimise the 8 valve (Emtron KV8, CDI, Clewett cam sensor, Milledge cam, SFR intake, 70mm tb, GTX3575R Gen II) etc.