My VW baja - potential rotary project
#126
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So I recently found out the bus trans has a drivetrain loss of around 20%. This is due to the hypoid gears they use which are less efficient but stronger than what's found in a bug trans. This means if I'm aiming for 100HP to the wheels, I'd need 120 to 130 HP at the flywheel with my bus trans. I was told 100 at the wheels is plenty. You can do a lot with just 100HP, they say. I don't doubt it, and I could have a peak HP at that level with a stock ported R5 13B pretty easily, but they were also assuming an air cooled VW engine. Those things make great low RPM torque. The HP is just the way they measure power over there for some reason. I thought you measure... torque? Problem is the rotary doesn't make that kind of torque at the same RPM. I need a way to get the low end grunt of a 2332 without the cost. So stock S5 turbo? I worked out some numbers. See if you can follow my math. 150hp x .2 = 30 150 - 30 = 120hp 160hp x .2 = 32 160 - 32 = 128hp 162.5hp x .2 = 32.5 162.5 -32.5 = 130hp For example, if the turbo makes a max of 150HP, with a 20% drivetrain loss, I'll have 120HP at the wheels. Likewise if I get 162.5HP at the flywheel, I'll have 130HP at the rear wheels. I think 150 to 160 HP is pretty realistic, actually, considering the stock S5 turbo made 200HP in an FC at stock boost levels and stock T2 spec intake and exhaust ports with a top mount IC. My baja engine has smaller ports and most likely won't have an intercooler. So I'm going from 200HP under factory intended conditions down to 150 to 160. Then factoring in a 20% drivetrain loss I'll get about 120 to 130HP at the wheels. I think that's realistic. And that's being generous. I think the actual numbers will be lower still. Like 100 to 110HP (but plenty of low end torque!). Thoughts?
#127
Sounds like you're not messing around. But streetport and semi p-port? You may be trying too hard. You can make 400HP on stock ports, you know. Oh well you know what you're doing, right? Go ahead and post some updates in your build thread, ok? Maybe we can change your mind about your combination port idea and just go with a healthy streetport or something. Your life will be a lot easier. Oh and twin aftermarket turbos? Really? I totally wouldn't. Sorry, better keep that kind of chatter to your build thread and keep this one baja centered.
#128
I have some good news.
Turns out the S5 turbo only boosts to 5.5psi without its stock ECU controlled boost solenoid hooked up. That's perfect for a low boost setup in the baja! Only as long as it gets a 2.5" exhaust and not a 3" one.
The reason I was seeing at least 7psi with this turbo in the brown car was due to boost creep! Oh noes! It's because of its full 3" exhaust!
So I decided to go with a Racing Beat thickwall 2.5" u-bend as a DP. This has an ID of 2.25" which is pretty small. Hopefully it'll tame the boost creep.
Turns out the S5 turbo only boosts to 5.5psi without its stock ECU controlled boost solenoid hooked up. That's perfect for a low boost setup in the baja! Only as long as it gets a 2.5" exhaust and not a 3" one.
The reason I was seeing at least 7psi with this turbo in the brown car was due to boost creep! Oh noes! It's because of its full 3" exhaust!
So I decided to go with a Racing Beat thickwall 2.5" u-bend as a DP. This has an ID of 2.25" which is pretty small. Hopefully it'll tame the boost creep.
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