17 replies to this topic

[Java_Green]

This probably won't be helpful, but hopefully enlightening.

Exhausts are not straightforward. What works on one engine extremely well may not be the optimal on the next. Even the smallest of changes - shape, dia, location of silencers, diameters, etc - all have big impacts. The only practical way you'll find out is to try a few. Bigger is not always better and what works in one power range, is not likely to work across the range.

 

A simple experiment you can try is to have a short section of exhaust made, say 4" long that fits on to the end of your current exhaust, slip that on and go for a drive.

 

 

As so many times before..., you are absolutely right and I am aware of the circumstances. I was more after a pointing in the right direction. On other engines (street engines tuned to different extent, 1293-1400cc), I have favoured the twin box, side exit RC40 system (1"3/4) with a std bore LCB. On this engine, I think it can result in to high gas speeds why I am considering bigger diameters.

 

[IronmanG]

This probably won't be helpful, but hopefully enlightening.

Exhausts are not straightforward. What works on one engine extremely well may not be the optimal on the next. Even the smallest of changes - shape, dia, location of silencers, diameters, etc - all have big impacts. The only practical way you'll find out is to try a few. Bigger is not always better and what works in one power range, is not likely to work across the range.

A simple experiment you can try is to have a short section of exhaust made, say 4" long that fits on to the end of your current exhaust, slip that on and go for a drive.

As so many times before..., you are absolutely right and I am aware of the circumstances. I was more after a pointing in the right direction. On other engines (street engines tuned to different extent, 1293-1400cc), I have favoured the twin box, side exit RC40 system (1"3/4) with a std bore LCB. On this engine, I think it can result in to high gas speeds why I am considering bigger diameters.

Try Stuart at Vmax. Seeing as he probably makes 90% of supercharged kits on the market he probably has a fair idea

[Cooperman]

Be very careful with the static compression ratio when going to forced induction.
If m, for example, the static CR is 9:1, with a max boost pressure of, say, 5 psi you are increasing the actual CR by 1.3 which will give an effective CR of 11.7:1. For that to work you will need a recurved distributor and some better pistons.
I once had to completely rebuild an engine which had been fitted with a turbocharger and which blew up after 8 miles. No calculations had been done, There was no calibration sheet for the turbocharger and it turned out that it was given 7 psi increase which was a factor of 1.5 on the basic CR. The distributor was standard as were the pistons. It cost a lot of money and time to rebuild it including having the turbocharger set to give 5 psi with a calibration certificate, a special Aldon distributor, Omega pistons with a bigger dish volume from the standard ones. The combustion chamber volumes were increased to give 8:1 static and thus 10.4:1 with the boost of 5 psi.
In the end it ran beautifully and reliably.
Too many people think that a turbocharger can just be bolted on and a few minor modifications made to the exhaust system.
In fact it is a detailed engineering exercise including a lot of measurement and calculation.
Superchargers are equally complex as the drive and driven pulleys have to be sized to give correct boost ratio.