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How Much Boost/hp/rpm Can 'stock' 998 Crank Take?


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#1 -IR-

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Posted 24 October 2016 - 10:59 AM

Heyhey guy and gals.

 

I've got a mini 850 project on the go and a spare 998 engine knocking about and I'm toying with building it up to be a nice little turbo unit but I'm wondering how much the stock crank can take before it blows up.

 

Rebuilt straightcut box, crosspin diff, +20 rebore, forged pistons and rods I'm assuming the first thing to go bang would be the crank. I'm not putting boost figures etc because I'm not wondering what my power output will be because those numbers aren't really what this project is about. 

 

Thanks in advance :)



#2 mini13

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Posted 24 October 2016 - 11:42 AM

umm the A+ 998 is actually pretty sturdy,

 

i know of one that did 150 hp and reved to 7500 running about 18 psi boost specs below

 

http://www.twin-turb...k/The Spec.html



#3 matty...

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Posted 24 October 2016 - 06:55 PM

I would say he crank is one of the last things to worry about. As long as you have a decent set of Pistons, a well rebuilt bottom end, fuelling setup correctly and suitable CR you'll have very reliable engine.

#4 -IR-

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Posted 24 October 2016 - 08:33 PM

Awesome, thanks for the replies.

I'm not chasing anywhere near that as I'd be happy with 90-110 if it's reliable. I'm tempted to run a slightly higher CR than most turbo build and less boost in a attempt to get the turbo to spool quicker.

#5 mini13

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Posted 24 October 2016 - 09:13 PM

sounds good, although be aware that boost is adictive!

 

9:1 and somthing like a GT1544 turbo should be good



#6 -IR-

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Posted 24 October 2016 - 09:45 PM

Exactly what I'm planning to go for and blow through with a boost prepped DHLA 40.

Unfortunately knowing me I'll drive it at a safe boost then get bored in a month and turn it up till I blow it then bankrupt myself building a twin turbo 1460 16 valve or something equally outrageous 😂

#7 matty...

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Posted 29 October 2016 - 08:38 AM

You'd be better off using an SU carb, far more simple with regards to plenums, and plenty of needles available to suit a turbo'd setup, so it'll be easier/cheaper to setup the fueling.

The SU's are good for well over 200HP so no worry about it being restrictive of power.

#8 -IR-

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Posted 31 October 2016 - 06:50 AM

Hmmm I see where you're coming from, I do have a friend who's offered to hook me up with a Weber and tuning for a steal though.

to be honest after driving a blown jag out here (holiday in California) I'm also considering going with a supercharger instead now because like I said I'm not going for a mad quick engine just a nice street build and I really like the way the supercharged engine pulled right from down low and so predictably.

#9 Icey

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Posted 03 November 2016 - 10:23 PM

Hmmm I see where you're coming from, I do have a friend who's offered to hook me up with a Weber and tuning for a steal though.


I heard a similar line from a friend at work when he bought a Mercedes luxobarge - "It's OK, a mate of mine works in a Merc garage, he will do the servicing at mates rates!"

 

12 months later his mate has a new job and his monstrous Merc has developed some expensive electrical problems. I wouldn't base a project that'll be with you for some time on what could be a very temporary benefit.






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