OhChit Posted October 10, 2005 Share Posted October 10, 2005 I have a Project that I'm working on. It's a non street car and due to engine bay clearence issues I am limited to engine width of no more then 29" wide. The Subaru 2.5 SOHC engine will just about clear but is a thight fit, my problem is that I plan on running a Turbo I have a STI 2.5 Block, the problem area is the Heads and Cams? Does anyone know who makes a Turbo cam for the 2.5 SOHC heads? or I can run the 2.2 Turbo heads and in doing so I can keep the total width of the engine around 27" wide. Does anyone have any experience with running the earlier 2.2 Turbo heads on a 2.5 Block? I know the heads will fit, my concerens are will I lose much power due to the older generation heads? Or will the heads be able to handle the increased power delivered by the 2.5 STI block? This engine will be running an after-market ECU so the computer and wiring harness shouldn't be an issue. Also who sells beefer valve springs etc for these applications? Sorry for all the questions, but you guys are the Subie-experts Jon Quote Link to comment Share on other sites More sharing options...
OhChit Posted October 11, 2005 Author Share Posted October 11, 2005 Help-ppp Anyone? Quote Link to comment Share on other sites More sharing options...
cookie Posted October 11, 2005 Share Posted October 11, 2005 but I think nobody is answering this because the general opinion of the board is that if you want a turbo engine you should buy one. The expense of conversion to get a reliable engine is pretty high. An entire JDM turbo engine is fairly reasonable compared to the cost of converting an engine. You might try Nasioc as I seem to recall a forced induction forum. Quote Link to comment Share on other sites More sharing options...
OhChit Posted October 11, 2005 Author Share Posted October 11, 2005 Mate thanks for your help, but I just can't beleive that this hasn't been done before successfully. And even more so that someone on here dosn't know if it can be done? As I mentioned, I'm limited to space issues and simply trying to utlize a 2.5 STI low compression block and a SOHC set of heads. Now it's just a choice weather to use the 2.2 Turbo heads and cams, or try to use the SOHC 2.5 heads and come up with some sort of cam? but I think nobody is answering this because the general opinion of the board is that if you want a turbo engine you should buy one. The expense of conversion to get a reliable engine is pretty high. An entire JDM turbo engine is fairly reasonable compared to the cost of converting an engine.You might try Nasioc as I seem to recall a forced induction forum. Quote Link to comment Share on other sites More sharing options...
vic/se Posted October 11, 2005 Share Posted October 11, 2005 Mate thanks for your help, but I just can't beleive that this hasn't been done before successfully. And even more so that someone on here dosn't know if it can be done? As I mentioned, I'm limited to space issues and simply trying to utlize a 2.5 STI low compression block and a SOHC set of heads. Now it's just a choice weather to use the 2.2 Turbo heads and cams, or try to use the SOHC 2.5 heads and come up with some sort of cam? I could add ....why a turbo when you plan to use regular heads? your set up gonna be restrictive and combustion chamber size may rise your compression beyond the limits of a turbo setup Quote Link to comment Share on other sites More sharing options...
OhChit Posted October 12, 2005 Author Share Posted October 12, 2005 Where does it say that I intend on running a standard Head? I'm trying to suplement the Turbo block with a converted 2.5 SOHC head and Turbo cams. If need be I'll have the 2.5 SOHC heads ported for better air flow. or I'll use a pair of 2.2 Turbo heads. Not even close to a standard head. I could add ....why a turbo when you plan to use regular heads? your set up gonna be restrictive and combustion chamber size may rise your compression beyond the limits of a turbo setup Quote Link to comment Share on other sites More sharing options...
blitz Posted October 12, 2005 Share Posted October 12, 2005 I think that if you bolt on the 2.2 heads, the compression is gonna jump a bit (smaller chamber). Not sure by how much. The 2.5 SOHC heads will work, but at the very least, re-working the exhaust ports would be a good thing. Not sure about the cam profile. Cobb claims that their "Street Performer" is a good match for a bolt-on turbo kit. I think they'll work you up a custom grind based on a specific need. Turbo 2.0: 240*/240* - 109.5 LDA N/A 2.5: 232*/236* - 113.5 LDA When I compare the WRX 2.0 against the N/A 2.5 SOHC, the biggest significant difference I can see is opening the intake 9 degree sooner and closing 1 degree sooner for the turbo cam. The exhaust valve is started 3 degrees earlier and held open 1 degree later. Quote Link to comment Share on other sites More sharing options...
OhChit Posted October 12, 2005 Author Share Posted October 12, 2005 Blitz. Thanks for the info and valve research opening and closing. I had already contacted Cobb Tuning and they mentioned that they do have a cam for the 2.5 but the person that I spoke to didn't know much about it, nor did they say that it will work with a Turbo. I'm waiting to speak with one of their tech guys. Actually the 2.2T heads will be the best fit due to their smaller size, after looking at them I think that I can port the combustion camber a little larger. Do you happen to have any comparison on the 2.2T valve opening and closing as compaired to the 2.0 T ... I'm also wondering if the 2.2 heads will hold up on the 2.5 STI block and will be able to handle higher boost of maybe 15-20 lbs. Do you know who sells stronger valve springs? Thanks Jon I think that if you bolt on the 2.2 heads, the compression is gonna jump a bit (smaller chamber). Not sure by how much. The 2.5 SOHC heads will work, but at the very least, re-working the exhaust ports would be a good thing. Not sure about the cam profile. Cobb claims that their "Street Performer" is a good match for a bolt-on turbo kit. I think they'll work you up a custom grind based on a specific need. Turbo 2.0: 240*/240* - 109.5 LDA N/A 2.5 232*/236* - 113.5 LDA When I compare the WRX 2.0 against the N/A 2.5 SOHC, the biggest significant difference I can see is opening the intake 9 degree sooner and closing 1 degree sooner for the turbo cam. The exhaust valve is started 3 degrees earlier and held open 1 degree later. Quote Link to comment Share on other sites More sharing options...
blitz Posted October 12, 2005 Share Posted October 12, 2005 Blitz.Thanks for the info and valve research opening and closing. I had already contacted Cobb Tuning and they mentioned that they do have a cam for the 2.5 but the person that I spoke to didn't know much about it, nor did they say that it will work with a Turbo. I'm waiting to speak with one of their tech guys. Actually the 2.2T heads will be the best fit due to their smaller size, after looking at them I think that I can port the combustion camber a little larger. Do you happen to have any comparison on the 2.2T valve opening and closing as compaired to the 2.0 T ... I'm also wondering if the 2.2 heads will hold up on the 2.5 STI block and will be able to handle higher boost of maybe 15-20 lbs. Do you know who sells stronger valve springs? Thanks Jon Just some rambling thought here to chew on: My knowledge is limited, but my intuition is good. I have a sneaking suspicion that the stock 2.5 SOHC cam profile advanced 4-6 degrees, in combination with slightly heavier springs and great attention to detail regarding the head head-work (ports, chamber, seats) will give you the best overall compromise between cost, reliability and FAT upper-mid torque/minimal lag. Use a medium-size turbo spun to a higher pressure in combination with a really good intercooler setup (this includes outside airflow to the I/C). Top-end HP might be down a bit, but turbo lag is a bigger enemy in a 5-speed AWD boxer-porker. Not having to spin to the redine will save the botton-end too. It's a good thing to have a motor that's forgiving of low-revs coming out of a corner, gets you through a season with no breakage and minimal refreshing. There was someone offering adjustable cam gears for the 2.5 SOHC, but I lost the http. A re-weld, aggressive-ramp, high-lift cam in combination with heavy springs is gonna make more top-end, but is gonna need more babysitting & TLC. Cobb's are re-welds. I think you'll bust the factory 2.5 STI shortblock before you bust any of the heads. What heads were used on the 22B? Re-worked 2.2turbo castings? I'm not sure. Here's links from my collection. These are from about two years back, there's probably several others worth checking out that I don't have here. There's gotta be nuggets in there somewhere. http://www.xcceleration.com http://www.renickmotorsports.com/oscommerce/catalog/ http://www.boxer4racing.com/ http://www.techworkseng.com/ http://www.axispowerracing.net/ http://www.pdm-racing.com/products/subaru_corner.html http://www.modacar.com/car/Subaru/Impreza/ http://www.forcedairtech.com/ http://www.rallispec.com/ http://www.mrtrally.com.au/ Quote Link to comment Share on other sites More sharing options...
blitz Posted October 12, 2005 Share Posted October 12, 2005 I have a sneaking suspicion that the stock 2.5 SOHC cam profile advanced 4-6 degrees, in combination with slightly heavier springs and great attention to detail regarding the head head-work (ports, chamber, seats) will give you the best overall compromise between cost, reliability and FAT upper-mid torque/minimal lag. A competition multi-angle valve job increases the effective duration. Free-flowing, straight-through exhaust with a medium diameter to hold velocity goes without saying. Some numbers (just off the top of my head) would be something in excess of 320 ft./lbs. over the entire range 3000-5000 RPM, but no greater than 280 HP at the top. It would fall flat on it's face at 5500 and wouldn't rev past 6000 if you tried. You could miss gears left and right and not lose the motor. That's good right? Without the cam advance, everything would move up by about 500 RPM. To get the big horsepower numbers, you'd have to go with bigger cam and bigger turbo. Check out Techworks Engineering Cams. Quote Link to comment Share on other sites More sharing options...
OhChit Posted October 12, 2005 Author Share Posted October 12, 2005 Blitz... Thanks alot. You da-man. I'll dig through those links that you posted, and between what I have been told, and can dig up in those threads I'm sure I'll come up with a happy solution. By the way, I've decided to go with the 2.5 STI block and a set of 2.5 SOHC Heads and valves. A T3-4 turbo, ported heads, after market ECU and AIM dash cluster. I've been told that the stock 2.5 cams will perform very well with this combo. I'm also going to need some Hi RPM's maybe red line of 6500. It's mostly the zero to top end that I need, as this car's going to see much of it's life on the 1\4 mile strip and some short rally tracks. Jon Quote Link to comment Share on other sites More sharing options...
blitz Posted October 13, 2005 Share Posted October 13, 2005 It's mostly the zero to top end that I need...Funny guy. Quote Link to comment Share on other sites More sharing options...
Stupidru Posted October 20, 2005 Share Posted October 20, 2005 Talk to Rob Zombie, he did it & its really cool. I seen it at the import show at Carlisle a couple of years ago. He dropped a na 2.2 w/ an add on turbo into an ea82 wagon. I think his user name is SubaFreak. Quote Link to comment Share on other sites More sharing options...
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