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3.8 engine upgrade. Anyone in this forum done this?

tyinsky

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Joined
29 Jun 2012
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Hoping a few who browse these pages have upped the capacity and can share their opinions/experience of increasing the capacity to 3.8 litres along the lines of the X51 engines.

I realise outright power figures can be achieved with other methods like remaps and exhausts - my car is around 290bhp with the help of Wayne Scofield. And I'm not particularly excited by fitting a lumpy aftermarket cam that could be a pig to drive in traffic.

Extra torque does interest me. Not yet had the car two years and it has already clocked up a lot of miles on road trips. North Coast 500 in Scotland, Wild Atlantic Way on Ireland's West Coast, over the French Alpes to Nice and back along Route Napoleon. Surely this is the type of thing that will suit the 3.8?
 
All engines are designed to provide the torque curve the project identifies as right for the model and the market etc.

To simplify a comples subject - it is reasonable to say that it is the breathing ability of the enginein a particular rev band that is what is crucial and the bigger the inlet and exhaust components = the bigger the flow capacity and therefore the higher the revs that the peak torque is obtained.

Variable cam timing and lift, variable inlet pipe connections etc have enabled designers to design for power at high revs and then get back torque at lower revs creating a wider than tradditional power band = good acceleration.

Increasing the capacity merely means that the enigne is like on that a designer would create to produce peak power at slightly lower revs (because the breathing parameters are the same but the flow amount higher).

So there are 2 benefits - (1) = slightly lower torque band (good for acceleration) (2) slightly more top end power because although the peak mass air flow might well be the same it is pushing down on a bigger piston area (or longer stroke - or both) and so even the same peak mass air flow = more power.

The biggest diference is usually the feel of mid range torque and sharper pick up.

Baz
 
Nice to see Baz posting again.
Loads of posts on Rennlist, no doubt you have looked.
General concensus is poor bang for buck but worth considering if new P&Cs required.
When I used to race class capacity limit was 1650cc. So we all did it apart from those who fitted an MGB block in an MGA and ground the 1800 on the block to look like 1600 (not me). That's racing where every little bit helps. On the road it's only worth the bragging rights imho.
 
This is all a bit high tech for me, but put into laymans terms. The 3.8 conversion when I last looked was at 10K euros plus VAT but NLA. ......... even if it was available, the price put me right off. :D
 
Endoman said:
When I used to race class capacity limit was 1650cc. So we all did it apart from those who fitted an MGB block in an MGA and ground the 1800 on the block to look like 1600 (not me). That's racing where every little bit helps. On the road it's only worth the bragging rights imho.

Some of us kept to 1622cc allowing for re-boring when required.
 
I agree that 3.8 to 3.9 is not so much of a difference to justify the cost - unless - that is - you already have scored bores and pistons and need new cylinders etc - when it becomes very little extra for a bit more mid range punch.

It is also more interesting for a 3.6 to 3.9 - especially if the engine needs rebuilding anyway.

It is not good practice to increase the capacity too much because the restrictions of the inlet and exhast system will limit peak bhp benefits and result in very sharp mid range take up.

Our conversions are therefore 3.4 to 3.7 and 3.6 or 3.8 to 3.9 which overall will give a good result.

We may experiment with larger increases later in 2018 but if so they would not be available until the end of that year and it is by no means certain that they would prove nicer to drive or faster than the present conversions yet would be more expensive requiring new crankshafts as well.

Baz
 
What about a supercharger conversion. Definitely increases the grunt, and better value (bang per buck) than the increased capacity.

Been driven in a 964 with a supercharger and that was very rapid in comparison to my 993, and the instantaneous shove back in your seat was fun.

Not sure how it stacks up pricewise or reliability/longevity etc, but maybe worth considering.

Anyone any experience of the installation or ownership proposition?
 
Thanks for all the replies. Baz, the technical explanation is very good :thumbs:

Supercharging is for someone else searching for big power gains and who likes the whining noise. Occasionally I experience too much whining from the passenger seat.

I've so far drawn the line at 3.8 in order to use the MAHLE product, and I like that there was a 3.8 offered originally. It's important to me the car remains enjoyable to drive. It's not going to be a track day weapon.

Someone here must have done a 3.8 build to their car? Given they are 20-years old, top ends fairly common due to the exhaust valves, leaks can appear everywhere and so on - surely it makes sense to rebuild the whole engine and be done with it for many more years? Is there some sort of 'Porsche Illuminati' rule involving black balls and 25 bag valuations keeping people at 3.6?
 
tyinsky said:
Supercharging is for someone else searching for big power gains and who likes the whining noise. Occasionally I experience too much whining from the passenger seat.

That reminds me of a Mini Cooper S with the supercharger that I had when they first came out. Of all the things I hated about that car (which was a lot), the whine of the supercharger was probably number one. Hopefully it's a very rare occurrence for anyone to spoil the glorious sound of a 993 engine with that horrible whining. :what: It would be as good a reason as any that I can think of for the illuminati to get busy with the tar and the feathers.
 
There are a few 3.8 kits out there. Consensus from over the Pond is to go for the Mahle RSR pistons and cylinders as these barrels are sturdier. They do require some work on the crank case to seat properly, but if you're going the 3.8 route, you might as well add that to work for reducing crank windage.

Seeing you launch your car off the line at the gymkhana , you're obviously happy living near the redline.
:D
 
Sutton said:
There are a few 3.8 kits out there. Consensus from over the Pond is to go for the Mahle RSR pistons and cylinders as these barrels are sturdier. They do require some work on the crank case to seat properly, but if you're going the 3.8 route, you might as well add that to work for reducing crank windage.

Seeing you launch your car off the line at the gymkhana , you're obviously happy living near the redline.
:D

I can still smell the clutch and tyres! :bandit:
 
We weren't standing that far away and could chew on the tyre smoke. You left two lovely black lines on the tarmac :thumb:

If it's torque you're after, there's no substitute for capacity. It's just a question of ££ and whether you think it's a worthwhile trade off.

Are you talking to Redtek/ 9M/ Hartech etc?
 
I have been thinking about going from 3.6 to 3.8.. as a long term plan as I wanted my 993 to be as close to RS spec I can get, looks and performance. Im more interested in mid range punch than top end speed. for me, blasting from 0 to 90mph feels GREAT.

right now Im getting looks right 1st and removing unnecessary weight from engine, aircon, seats etc Im sure it will make it feel faster :D :hand:
 
I haven't owned but have driven a 964 3.8 conversion, to be honest I couldn't feel much difference, but if you're having to replace pistons and cylinders anyway then the only downside is the cost, 3.6 pistons and cylinders £3600
3.8's are £5400, that's a big price increase for what is closer to a 3.7 than a 3.8 3.8's are 3740cc or there abouts.

Bang for buck is not very good, but if money is no object.
 
Whilst I can see the attraction of staying OEM, this long redundant performance kit apparently yields little in terms of real world gain. It costs mental money as well. Even if you sourced the parts and got somewhere reputable to fit, it's still not going to be perceived as a factory build, which may or may not matter. If you were hell bent on more aircooled performance without swapping to a 993 Turbo, then I think I'd be researching big name companies who are making their living upping the air cooled NA ante. It's going to be big money though.

I remember a Rennlist thread where a company were working on a California compliant air cooled 400hp motor. Wonder what happened to that?
 

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