Turbo on a stroked motor

O

ogio855

Registered
Why is it so bad?
Long story short I have acquired a very highly spec'd motor with a 72mm stroke and stock bore. They are fairly "built" as is but run NA.
Goal was to use what I have without doing a crank swap to run a turbo setup, only looking for 280HP, max 300. Makes 225 as-is at 13.5:1 comp.
Thoughts were low comp pistons, ported head, refresh the other components that need it upon disassembly and call it a day. Could toss in an overbore idea as well if we want but that is up in the air.

FYI it is based on a gen2, runs the standard 18mm piston pin with ZX14 big end bearings on the rods, SS valves, heavier springs (unsure pressure), overdrive oil pump, heavy clutch springs, undercut gears, dry sump. Interestingly no spacer plate under the cylinders...

Cams are not stock but I don't know what cams are in it, I'm not smart enough to do much other than measure the lift and look for any identification marks on them. They look aftermarket, and the gears appear to be hand welded into position on the end of them.

It's a spec series race motor with less than 1000mi on it, internally it looks pretty good, but it was removed due to needing a rebuild from hours/mileage.

If it is an absolute no go on the stroker turbo it would be more financially viable to rebuild this current motor to its original spec and sell it for a stock Busa motor and just throw everything at that.
 
ogio855 said:
Why is it so bad?
Long story short I have acquired a very highly spec'd motor with a 72mm stroke and stock bore. They are fairly "built" as is but run NA.
Goal was to use what I have without doing a crank swap to run a turbo setup, only looking for 280HP, max 300. Makes 225 as-is at 13.5:1 comp.
Thoughts were low comp pistons, ported head, refresh the other components that need it upon disassembly and call it a day. Could toss in an overbore idea as well if we want but that is up in the air.

FYI it is based on a gen2, runs the standard 18mm piston pin with ZX14 big end bearings on the rods, SS valves, heavier springs (unsure pressure), overdrive oil pump, heavy clutch springs, undercut gears, dry sump. Interestingly no spacer plate under the cylinders...

Cams are not stock but I don't know what cams are in it, I'm not smart enough to do much other than measure the lift and look for any identification marks on them. They look aftermarket, and the gears appear to be hand welded into position on the end of them.

It's a spec series race motor with less than 1000mi on it, internally it looks pretty good, but it was removed due to needing a rebuild from hours/mileage.

If it is an absolute no go on the stroker turbo it would be more financially viable to rebuild this current motor to its original spec and sell it for a stock Busa motor and just throw everything at that.
Click to expand...
Hi. I have a 2mm Marine crank and 10 to 1 pistons. I will be running up to 60 lbs of boost in race tune with VP M1 fuel.
 
ogio855 said:
Why is it so bad?
Long story short I have acquired a very highly spec'd motor with a 72mm stroke and stock bore. They are fairly "built" as is but run NA.
Goal was to use what I have without doing a crank swap to run a turbo setup, only looking for 280HP, max 300. Makes 225 as-is at 13.5:1 comp.
Thoughts were low comp pistons, ported head, refresh the other components that need it upon disassembly and call it a day. Could toss in an overbore idea as well if we want but that is up in the air.

FYI it is based on a gen2, runs the standard 18mm piston pin with ZX14 big end bearings on the rods, SS valves, heavier springs (unsure pressure), overdrive oil pump, heavy clutch springs, undercut gears, dry sump. Interestingly no spacer plate under the cylinders...

Cams are not stock but I don't know what cams are in it, I'm not smart enough to do much other than measure the lift and look for any identification marks on them. They look aftermarket, and the gears appear to be hand welded into position on the end of them.

It's a spec series race motor with less than 1000mi on it, internally it looks pretty good, but it was removed due to needing a rebuild from hours/mileage.

If it is an absolute no go on the stroker turbo it would be more financially viable to rebuild this current motor to its original spec and sell it for a stock Busa motor and just throw everything at that.
Click to expand...

If you only are looking for 300HP, you wont need to do anything at all to the engine. you could literally just boost what you have now. You will however have a very high TQ, so be aware of the potential issues. You dont mention fuel, but at that power level any normal higher octane race fuel would suffice, even at 13.5:1 compression. That said, you will likely be better off using a set of drop in low compression turbo pistons. They will still be somewhere in the 10:1 range with your stroke, but you will literally only need to tickle the engine with positive pressure to make the power you want.
As mentioned, Tq will be really high with this, It is sort of odd to use a large stroke and only 300hp but it should work.

John
 
Dustin02 said:
Stroker will be fun with a turbo. You just don't want to overbore with a turbo due to head gasket sealing surface is smaller.

As for cams, if you can't spec them, then maybe some known spec cams would be better.
Click to expand...
+2mm overbore (83mm) is fine for turbo use. I have seen no detriment over 81mm bore in applications at the 700HP+ range.

John
 
sportbikeryder said:
If you only are looking for 300HP, you wont need to do anything at all to the engine. you could literally just boost what you have now. You will however have a very high TQ, so be aware of the potential issues. You dont mention fuel, but at that power level any normal higher octane race fuel would suffice, even at 13.5:1 compression. That said, you will likely be better off using a set of drop in low compression turbo pistons. They will still be somewhere in the 10:1 range with your stroke, but you will literally only need to tickle the engine with positive pressure to make the power you want.
As mentioned, Tq will be really high with this, It is sort of odd to use a large stroke and only 300hp but it should work.

John
Click to expand...
John,

Appreciate this info. This is the ideal scenario we're looking at. I'll try not to overthink it all and just do a quick refresh on the motor and see where it takes it with some low comp pistons.

I currently run on a mix of 114 leaded race fuel and 94 octane pump (25/75)%. That's an easy to obtain and economically viable option to continue with as well. If it would be possible to tune it to 94 pump only that would be even easier. But getting that race fuel isn't impossible. (it's about 3hrs away but I'm up for work often enough to stock up)

It is a car application so the concern with going over the 300HP is gearbox life. Which is currently the primary factor limiting motor life, and the reasons for the low mileage rebuild recommendations.
 
ogio855 said:
John,

Appreciate this info. This is the ideal scenario we're looking at. I'll try not to overthink it all and just do a quick refresh on the motor and see where it takes it with some low comp pistons.

I currently run on a mix of 114 leaded race fuel and 94 octane pump (25/75)%. That's an easy to obtain and economically viable option to continue with as well. If it would be possible to tune it to 94 pump only that would be even easier. But getting that race fuel isn't impossible. (it's about 3hrs away but I'm up for work often enough to stock up)

It is a car application so the concern with going over the 300HP is gearbox life. Which is currently the primary factor limiting motor life, and the reasons for the low mileage rebuild recommendations.
Click to expand...
For a car application, I would look at a small turbo so it will have a very low boost threshold. When combined with the 1484cc engine with teh long stroke, it should work well. Cams can probably be pretty much anything form stock to a wild all motor cam, but that said, you may have some valve spring and tappet issues if you have a high lift and want to run for a long time.
If you are able to go with an intercooled system, you can very likely just run pump gas if you keep the compression fairly low. You will want to pay attention to low rpm / high load situations and adjust ignition timing accordingly to prevent knock during hard acceleration.

John
 
Have always wanted a 5mil stroker with 83mm but worried about head gasket sealing. Street would be a blast My “B” motor which is quickly becoming my A motor. I have a gen two crank sized and ready. Working on the gearbox. First ever undercut Done by me. Have been too work and life to do 3-6. But I have done 1-2. Head is 1mil O/S valve HMP head
 
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