forcefed86
Member
- Joined
- Jul 28, 2005
I’ve been snooping around the small engine boards and keep running into huge power being made with very little timing and very high boost. I thought it odd I’ve never seen low timing and much over 20psi in the larger V6-V8 engine community, but it’s very common to see high timing and low boost. I've even heard multiple "guru" buick racers claim anything less than 18* of timing is pointless. Yet the 2.0 liter guys are running negative timing numbers at peak torque and single digit timing numbers up top making incredible power per cubic inch.
For example…
There are currently several DSM (2.0 4cyl) guys running 60mm holset hx40 turbos into the 37-43psi range and making 600-700 Awhp.(e85) None of them run over 18* of timing up top (usually around 16 or less). Some on 100% factory short blocks as well.
The few that I have spoken to run -5 to 8* at peak torque. For example this is the OEM timing map for an Evo 9.
As you can see timing is crazy low. Close friend runs this exact map on pump fuel (93) on his hx40 powered mitsubishi 2.3 liter at over 30psi of boost. He is well into the low 10 second range approx 550-575whp going by vehicle weight.
Personally I only run 18* at wot with my buick engine. I do however run 28-30psi (e85). Initially I tried 25* timing and would see knock right around 23-23 psi. I pulled timing and upped boost and my trap speed kept rising. I tried to push this farther, but I believe I'm having valve float at anything above 30psi in the upper revs. (110lb springs, factory valvetrain).
Is that only a "trick" that can be accomplished with newer/better designed heads and twin cam designs? Or does the smaller displacement in some way allow for the much higher manifold pressures?
I guess my question would be at what point will lowering timing and raising boost yield diminishing results? And if boost will make more power than timing, why don’t larger displacement guys run higher boost and lower timing?
For example…
There are currently several DSM (2.0 4cyl) guys running 60mm holset hx40 turbos into the 37-43psi range and making 600-700 Awhp.(e85) None of them run over 18* of timing up top (usually around 16 or less). Some on 100% factory short blocks as well.
The few that I have spoken to run -5 to 8* at peak torque. For example this is the OEM timing map for an Evo 9.
As you can see timing is crazy low. Close friend runs this exact map on pump fuel (93) on his hx40 powered mitsubishi 2.3 liter at over 30psi of boost. He is well into the low 10 second range approx 550-575whp going by vehicle weight.
Personally I only run 18* at wot with my buick engine. I do however run 28-30psi (e85). Initially I tried 25* timing and would see knock right around 23-23 psi. I pulled timing and upped boost and my trap speed kept rising. I tried to push this farther, but I believe I'm having valve float at anything above 30psi in the upper revs. (110lb springs, factory valvetrain).
Is that only a "trick" that can be accomplished with newer/better designed heads and twin cam designs? Or does the smaller displacement in some way allow for the much higher manifold pressures?
I guess my question would be at what point will lowering timing and raising boost yield diminishing results? And if boost will make more power than timing, why don’t larger displacement guys run higher boost and lower timing?