Longer or shorter stroke on a turbo application?
Thread Starter
Joined: Nov 2004
Posts: 998
Likes: 19
From: Rotterdam, New York
Longer or shorter stroke on a turbo application? I have heard/read for the last 15+ years that turbos liked big bore and short stroke. I am seeing more stroker combos running ridiculous times with relatively small turbos than ever. What are the benefits and down sides of using a longer or shorter stroke with all else being equal?
For a baseline, let's assume a forged 6.0 block and stock 317 casting heads using around an 84-88mm single turbo and a t6 exhaust with an auto weighing in between 3600 and 3800 pounds street/strip application.
Please discuss......
For a baseline, let's assume a forged 6.0 block and stock 317 casting heads using around an 84-88mm single turbo and a t6 exhaust with an auto weighing in between 3600 and 3800 pounds street/strip application.
Please discuss......
Thread Starter
Joined: Nov 2004
Posts: 998
Likes: 19
From: Rotterdam, New York
My car is heavy, but it runs a 275 drag radial pro tire with no bars so I am thinking I will have to limit power down low anyway. Between the transbrake, boost controller and PTC converter I am hoping I can dial in the amount of power I need off the line either way. I was only planning on spinning it to 6500 rpm.
I'm just trying to make the combo as efficient as possible so I only have to build it once and all these recent stroker combos running great times was making me second guess myself. I have never seen a compressor map for a Forced inductions S484 with a 1.32 T6 housing, and even if I did I haven't plotted a combo on one for about 12 years so I doubt I remember how. Not sure where a 365ci or 403ci would fall on that map at those rpm.
I'm just trying to make the combo as efficient as possible so I only have to build it once and all these recent stroker combos running great times was making me second guess myself. I have never seen a compressor map for a Forced inductions S484 with a 1.32 T6 housing, and even if I did I haven't plotted a combo on one for about 12 years so I doubt I remember how. Not sure where a 365ci or 403ci would fall on that map at those rpm.
i only wanted to rev to around 6500 as well, so i went 4in. stroke inna ls3, on a street car i was lookin for a lil more power down low, also havva trans brake for the track but more cubic inch will reduce lag as well. track car only.. id go shorter stroke for rpm and who cares about lag.. but street car ima take all the cubic inch i can get and stuff it inna turbo 😈
Stroker cranks are everywhere. Short stroke are hard to find. I wanted a 4.125 bore 3.268 stroke but couldn't find a crank without a 3-6 month wait attached. Shortest i could find available was a 3.75, so that's what i went with. Car will weigh about 3250 with me in it. Rarely at the track.
Launching!
Joined: Oct 2006
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From: Grand Rapids, MI
In very high performance applications, turbochargers generally respond better to stroke increases than they do bore increases. In a mild street/strip build like you're proposing, you would likely not be able to see much difference from going each route individually.
Jack
Jack
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From: Norn Iron
Stroker cranks are everywhere. Short stroke are hard to find. I wanted a 4.125 bore 3.268 stroke but couldn't find a crank without a 3-6 month wait attached. Shortest i could find available was a 3.75, so that's what i went with. Car will weigh about 3250 with me in it. Rarely at the track.
Although I think the 4.8 crank is around 3.2" or so ?
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Verdad Gallardo Even a stock stroke aftermarket crankshaft can be hard to find. June of last year I had to settle for a 3.75 or wait. 6 weeks for a Lunati was the best quote I got. A 6 week quote for a specialty part can easily turn into 6 months.
I ordered a 3.268 from Callies(really nice people by the way), they had it in stock and I wanted the machined reluctor wheel installed. After about 4 weeks I called to check on it and they discovered they didn't have one and it would be a while before they made any more. Fortunately i was able to return my 6.3" connecting rods and get a 3.75" Magnum along with 6.125" rods. Just one of those little things that come up with engine stuff.
TECH Apprentice
Joined: Feb 2014
Posts: 328
Likes: 1
From: Baton Rouge La
I have heard/read for the last 15+ years that turbos liked big bore and short stroke. I am seeing more stroker combos running ridiculous times with relatively small turbos than ever. What are the benefits and down sides of using a longer or shorter stroke with all else being equal?
For a baseline, let's assume a forged 6.0 block and stock 317 casting heads using around an 84-88mm single turbo and a t6 exhaust with an auto weighing in between 3600 and 3800 pounds street/strip application.
Please discuss......
For a baseline, let's assume a forged 6.0 block and stock 317 casting heads using around an 84-88mm single turbo and a t6 exhaust with an auto weighing in between 3600 and 3800 pounds street/strip application.
Please discuss......
I would love to put a 4.8 crank in a 6.0... I've always loved short stroke engines as they love rpm, and tend to make power up high better.
That would actually come to a 5.4... Which would be perfect in my mustang.
That would actually come to a 5.4... Which would be perfect in my mustang.
Thread Starter
Joined: Nov 2004
Posts: 998
Likes: 19
From: Rotterdam, New York
Thank you everyone for the replies. So what I have gathered from the replies is a boosted engine responds to stroke basically the same way an NA engine will. I have been building and racing big block Chevies for almost 25 years. This will be my first small block turbo combo so it's a whole new learning experience. 
Not mine but here are some amazing results for destroked 6.0 resulting in a 5.4 using a 4.8 crank
https://ls1tech.com/forums/dynamomet...8tq-video.html
https://ls1tech.com/forums/dynamomet...8tq-video.html
Last edited by 2muchboostNY; Feb 9, 2015 at 10:31 AM.
If you're considering doing this to to your 6.0, assuming it's an iron block, I definitely wouldn't go with a larger stroke than stock, as iron 6.0 blocks have shorter cylinder walls and at the bottom of the stroke some of the piston hangs out of the cylinder (With a longer than stock stroke). A de-stroked 6.0 would be SWEET!
Registered User
Joined: Feb 2015
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Who ever said that probably heard that from someone that did not know what they wre talking about. A turbo does not know if it like a short stroke or a long stroke. It all depends on what you are trying to achieve. It's really not the stroke it's the rod ratio. How ever longer strokes usually have a lower Rod ratio so they are better for a lower power range. So if you want to power from 3500 to 6500 a 1.5 Rod ratio will work better than a 1.7 Rod ratio. A 1.7 will work better from 4500 to 8000 so it all depends how you want to preform.
