wylin
08-01-2002, 11:33 AM
heres sum 2.5 imprezza technical info i got from SAe from the socal imprezza club for karizma when she was considering an imprezza.
Only MY 98 models came with DOHC
MY99~01 models have SOHC
98 DOHC are unreliable Turbo engines...worst turbo motor
MY99 has 9.7:1 compression ratio and uses MAF
MY00~01 has 10.0:1 compression ratio and uses MAP
MY99 just had MAF recalled which i replaced last week
SOHCs are better on EJ25... as far as stock motor turbo mod goes... MY99 SOHCs are probably best bet since compression is lower.
The 2.5 DOHC engine is a "stretched" design engine and is not recommended for more than 235hp. The cases of this engine are strong enough to run for ever at 165hp, but are not designed for 300hp. So, until proven otherwise, we are recommending that the DOHC 2.5 keep its stock pistons and compression ratio and be limited to about 240hp on pump gas. Supercharging is idea for this low pressure boost, 5-7 pounds scenario.
The weakest link in the 2.5 motor is the crankshaft connecting rods. The end caps are too thin to take a lot of stress. The stress can be rotational or due to high power output. We recommend moving the red line down to 5200 rpm when going to 220hp output levels. This will keep the bottom end out of harm's way. As many of you know a 2.5 engine running flat at 130pmh+ lost a rod bearing this spring. Like, what did we say about this before, guys?
For those wanting the "Big Power", as a friend of mine calls it, these US engines need a change of pistons to lower the compression down to 8.5:1 or so. Then is is fairly easy to get 300hp from the the 2.5 SOHC engine with some hope of reliability. We are holding our breath on the reliability of the 2.5 DOHC at these higher outputs. As I said earlier, lower your red line and install an oil cooler. Do not get greedy with the boost. All boost junkies suffer the same fate: engine damage sooner or later.
[b:adf3d67f8d]Feedbak comments and is it just me or WRX ppl are cocky and i needa spank them all. w/ RWD 2.0 turbo power. =P[/b:adf3d67f8d]
[img:adf3d67f8d]http://www.isrperformance.com/decals2a.jpg[/img:adf3d67f8d]
Only MY 98 models came with DOHC
MY99~01 models have SOHC
98 DOHC are unreliable Turbo engines...worst turbo motor
MY99 has 9.7:1 compression ratio and uses MAF
MY00~01 has 10.0:1 compression ratio and uses MAP
MY99 just had MAF recalled which i replaced last week
SOHCs are better on EJ25... as far as stock motor turbo mod goes... MY99 SOHCs are probably best bet since compression is lower.
The 2.5 DOHC engine is a "stretched" design engine and is not recommended for more than 235hp. The cases of this engine are strong enough to run for ever at 165hp, but are not designed for 300hp. So, until proven otherwise, we are recommending that the DOHC 2.5 keep its stock pistons and compression ratio and be limited to about 240hp on pump gas. Supercharging is idea for this low pressure boost, 5-7 pounds scenario.
The weakest link in the 2.5 motor is the crankshaft connecting rods. The end caps are too thin to take a lot of stress. The stress can be rotational or due to high power output. We recommend moving the red line down to 5200 rpm when going to 220hp output levels. This will keep the bottom end out of harm's way. As many of you know a 2.5 engine running flat at 130pmh+ lost a rod bearing this spring. Like, what did we say about this before, guys?
For those wanting the "Big Power", as a friend of mine calls it, these US engines need a change of pistons to lower the compression down to 8.5:1 or so. Then is is fairly easy to get 300hp from the the 2.5 SOHC engine with some hope of reliability. We are holding our breath on the reliability of the 2.5 DOHC at these higher outputs. As I said earlier, lower your red line and install an oil cooler. Do not get greedy with the boost. All boost junkies suffer the same fate: engine damage sooner or later.
[b:adf3d67f8d]Feedbak comments and is it just me or WRX ppl are cocky and i needa spank them all. w/ RWD 2.0 turbo power. =P[/b:adf3d67f8d]
[img:adf3d67f8d]http://www.isrperformance.com/decals2a.jpg[/img:adf3d67f8d]