2.5L shortblock from RalliSpec
Thread Starter
Big Baller
iTrader: (1)
Joined: Nov 2002
Posts: 1,821
From: Washington
Car Info: 93 BG5, 00&01 GM6, 06LGT, 07STi
2.5L shortblock from RalliSpec
Here is the email I sent them and thier reply:
They responded with:
Most important things here I think are items 1&2
If I can get Ed to cc a 2.5RS head and an STi head then we can figure out the compression ratios.
I figure I'm on to something here....
Hello!
My name is Dominic Acia.
I'm an i-clubber and subaru nut. I have a 2001 2.5RS that I turbocharged with a Ludespeed turbo kit.
I am looking for a 2.5L shortblock to use with my stock heads.
I had contemplated the use of a USDM STi shortblock, but I have a list of concerns:
1. Valve reliefs in the STi pistons not matching my configuration.
2. Compression Ratio. I'm looking to get a CR of 9 to 9.5:1
3. Rod length. I don't want shorter rods than my standard 2.5. Everyone knows that longer rods increase piston dwell and give better power figures. I read somewhere that the STi rods are shorter.
So my question is: Does my desired shortblock exist?
I'm looking to create 350-450HP on a medium compression (9:1 to 9.5:1), medium boost (10-14lbs) engine. It was my understanding that the stock rods can't handle >350HP.
I'm looking for a semi-closed deck block also.
Any help or guidance you can provide will be greatly appreciated.
Thank you for your time,
Dominic Acia
My name is Dominic Acia.
I'm an i-clubber and subaru nut. I have a 2001 2.5RS that I turbocharged with a Ludespeed turbo kit.
I am looking for a 2.5L shortblock to use with my stock heads.
I had contemplated the use of a USDM STi shortblock, but I have a list of concerns:
1. Valve reliefs in the STi pistons not matching my configuration.
2. Compression Ratio. I'm looking to get a CR of 9 to 9.5:1
3. Rod length. I don't want shorter rods than my standard 2.5. Everyone knows that longer rods increase piston dwell and give better power figures. I read somewhere that the STi rods are shorter.
So my question is: Does my desired shortblock exist?
I'm looking to create 350-450HP on a medium compression (9:1 to 9.5:1), medium boost (10-14lbs) engine. It was my understanding that the stock rods can't handle >350HP.
I'm looking for a semi-closed deck block also.
Any help or guidance you can provide will be greatly appreciated.
Thank you for your time,
Dominic Acia
Dominic,
1. Valve sizing is very similar between STi 2.5L and 2.5RS...however, the included angle between the valves is different which may possibly affect the ideal valve relief dimensions although I doubt it.
2. Combining the US WRX 2.0L heads with the STi 2.5L shortblock results in a 8.6:1 compression ratio. I am not quite sure what the 2.5RS heads would be but could do some research to find out. My guess is that it may be as high as 9:1 like you are looking for but I need to measure the head volume to find out.
3.STi 2.5L has approx. 2.5mm shorter rod length to allow for changes to the piston in order to increase strength and improve ring land heat transfer path. The normally aspirated piston design has some problems with regards to top ring land failures.
4. Stock rods are not recommended for very high horsepower applications unless they are properly blueprinted, stress-relieved, and shotpeened. For the cost it is worthwhile to just go with aftermarket rods.
We can put together a custom built 2.5L shortblock to meet your needs. We would use the STi semi-closed deck block w/ custom aftermarket pistons and rods. Total delivery time on this would be 8-10 weeks. Thanks.
Regards,
Dave
RalliSpec
1. Valve sizing is very similar between STi 2.5L and 2.5RS...however, the included angle between the valves is different which may possibly affect the ideal valve relief dimensions although I doubt it.
2. Combining the US WRX 2.0L heads with the STi 2.5L shortblock results in a 8.6:1 compression ratio. I am not quite sure what the 2.5RS heads would be but could do some research to find out. My guess is that it may be as high as 9:1 like you are looking for but I need to measure the head volume to find out.
3.STi 2.5L has approx. 2.5mm shorter rod length to allow for changes to the piston in order to increase strength and improve ring land heat transfer path. The normally aspirated piston design has some problems with regards to top ring land failures.
4. Stock rods are not recommended for very high horsepower applications unless they are properly blueprinted, stress-relieved, and shotpeened. For the cost it is worthwhile to just go with aftermarket rods.
We can put together a custom built 2.5L shortblock to meet your needs. We would use the STi semi-closed deck block w/ custom aftermarket pistons and rods. Total delivery time on this would be 8-10 weeks. Thanks.
Regards,
Dave
RalliSpec
If I can get Ed to cc a 2.5RS head and an STi head then we can figure out the compression ratios.
I figure I'm on to something here....
Thread Starter
Big Baller
iTrader: (1)
Joined: Nov 2002
Posts: 1,821
From: Washington
Car Info: 93 BG5, 00&01 GM6, 06LGT, 07STi
some "guru's" over there claim between 8.6 and 9:1 compression.
So does rallispec.
So it looks like I'm probably going to go that route...
Then I'll up the boost a few hundred pounds...
I'm pretty sure my turbo will handle 450HP.
.63 turbine and .60 compressor.
How much do you think dropping my compression over one point will hurt my lag?
So does rallispec.
So it looks like I'm probably going to go that route...
Then I'll up the boost a few hundred pounds...
I'm pretty sure my turbo will handle 450HP.
.63 turbine and .60 compressor.
How much do you think dropping my compression over one point will hurt my lag?
Thread Starter
Big Baller
iTrader: (1)
Joined: Nov 2002
Posts: 1,821
From: Washington
Car Info: 93 BG5, 00&01 GM6, 06LGT, 07STi
of course the S80 is setting back my suby plans about two months. My bonus went to a down payment instead of injectors and gauges... oh well...
i think with the 2.5L and with 8.5-9:1 compression, turbo spool will be goo, the benefit of being able to run higher boost will negate any small lag you'd gain with a little lower compression. Do you have a ball bearing turbo?
Thread Starter
Big Baller
iTrader: (1)
Joined: Nov 2002
Posts: 1,821
From: Washington
Car Info: 93 BG5, 00&01 GM6, 06LGT, 07STi
Originally posted by Nolimit
. Do you have a ball bearing turbo?
. Do you have a ball bearing turbo?
I'll have to check that out...
It's the Ludespeed stage III turbo.
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