15 April 2006, 09:13
I would agree that it would be easier to reach 250 HP with a B230FT motor than with a B21ET motor. The larger displacement and the higher static compression ratio of the B230FT will help to make it easier.
If you are going to rebuild the B230FT, then install B230ET pistons [they have a smaller dish which will raise the SCR a bit more. And set the piston deck height to achieve a squish clearance of 0.030in [0,75mm].
Tight squish raises the detonation threshhold: you can either run more boost before it pings; or you can use lower octane fuel at the same boost level that you were using higher octane gasoline for.
If you can find one of the L block B230FTs [that has the piston oil squirters], that would be even better. Piston cooling helps protect the pistons from the heat. And cooler pistons are stronger pistons because aluminum gets weaker as it gets hotter.
I have built 2 B230FT motors using the B230ET pistons, and having squish clearances of 0.037in on the first one; and 0.035in on the second motor. The static compression ratio [SCR] of both motors is right at 10:1. They both run very well at 8-10 PSI of boost on 87 octane [(RON+ MON)/2 USA gasoline].
I built a third B230FT motor using the B230FT deep dish pistons, and set the squish clearance at 0.030in. That resulted in a SCR of about 9.4:1. That motor also runs well on 87 octane. But I can tell a slight difference in performance because of the lower SCR. To do it over again, I would put the ET pistons in that motor as well.
The old rule of running with a low SCR and using a higher boost setting to make up for the low SCR is becoming outdated. If you set up the motor to have tight squish, the SCR is not as much a worry when it comes to running more boost.
Tight squish improves the in-cylinder turbulence and promotes fastburn. That helps to reduce the tendency to detonate that can occur when the combustion of the air/fuel mix in the cylinder proceeds slowly.
Tight squish works.
My next motor build, when I can find the time to do it because it is for myself, will be a B21FT using B21F flattop pistons and a squish clearance of about 0.024in. I calculate the SCR will be about 10.5:1. And I expect to be able to run 10-15 PSI on 87 octane without detonation.
TF
If you are going to rebuild the B230FT, then install B230ET pistons [they have a smaller dish which will raise the SCR a bit more. And set the piston deck height to achieve a squish clearance of 0.030in [0,75mm].
Tight squish raises the detonation threshhold: you can either run more boost before it pings; or you can use lower octane fuel at the same boost level that you were using higher octane gasoline for.
If you can find one of the L block B230FTs [that has the piston oil squirters], that would be even better. Piston cooling helps protect the pistons from the heat. And cooler pistons are stronger pistons because aluminum gets weaker as it gets hotter.
I have built 2 B230FT motors using the B230ET pistons, and having squish clearances of 0.037in on the first one; and 0.035in on the second motor. The static compression ratio [SCR] of both motors is right at 10:1. They both run very well at 8-10 PSI of boost on 87 octane [(RON+ MON)/2 USA gasoline].
I built a third B230FT motor using the B230FT deep dish pistons, and set the squish clearance at 0.030in. That resulted in a SCR of about 9.4:1. That motor also runs well on 87 octane. But I can tell a slight difference in performance because of the lower SCR. To do it over again, I would put the ET pistons in that motor as well.
The old rule of running with a low SCR and using a higher boost setting to make up for the low SCR is becoming outdated. If you set up the motor to have tight squish, the SCR is not as much a worry when it comes to running more boost.
Tight squish improves the in-cylinder turbulence and promotes fastburn. That helps to reduce the tendency to detonate that can occur when the combustion of the air/fuel mix in the cylinder proceeds slowly.
Tight squish works.
My next motor build, when I can find the time to do it because it is for myself, will be a B21FT using B21F flattop pistons and a squish clearance of about 0.024in. I calculate the SCR will be about 10.5:1. And I expect to be able to run 10-15 PSI on 87 octane without detonation.
TF