Rotrex Superchargers

[Yazza54]

Butter Face said:

Thanks for the input, this is what I’m struggling with, if I’m already using all that the supercharger can do, why am I hitting just 0.6 bar of boost when the C30-94 should be a lot more?

Is your intercooler bigger than it needs to be? Associated piping large bore and long etc?

[stevieturbo]

Butter Face said:

Thanks for the input, this is what I’m struggling with, if I’m already using all that the supercharger can do, why am I hitting just 0.6 bar of boost when the C30-94 should be a lot more?

And why do you believe there should be more ?

Are there other people with the same engine/setup/blower/gearing making more boost ?

If so then you either have a leak or belt slip.

What does a graph of boost vs rpm look like ?

[Kccv23highliftcam]

Really interesting subject. [hope that ain't the kiss of death]

[Butter Face]

stevieturbo said:

And why do you believe there should be more ?

Are there other people with the same engine/setup/blower/gearing making more boost ?

If so then you either have a leak or belt slip.

What does a graph of boost vs rpm look like ?

To answer the questions as well as I can:

Because I have been told so, the C30-94 with a 110mm pulley should do 13-14psi (as I've been told) but there is so much conflicting information online that it's virtually impossible to know what the correct information is.

I have a friend with the same top mounted C30-94, 110mm pulley like mine, and his is doing 12psi and 383bhp. He has a front mount like I do but has a full manifold/decat/3inch exhaust whereas I have the standard manifold/exhaust but with a decat.

I have checked for leaks and none found, but never rule it out. Belt slip doesn't seem to be an issue, standard tensioner is normally fine but I do actually have a manual one to replace it.

Only information I have is the technical sheet from rotrex here - https://www.google.com/url?sa=t&rct=j&q=&a... if that helps!

I try an understand as I can, but this is all confusing the hell out of me!

[PeterBurgess]

Don't forget the pressure you are measuring is the bottleneck in the inlet manifold. If you fit a modified head which works you will record lower pressure in the manifold. If you fit daft overlap cams or bug*er up the cam timing you can reduce the pressure too.
If everything is the same as your mates then, as Stevie says, you must have belt slip, a leak or even a worn out compressor or a combination of these
Peter

[Butter Face]

Thanks Peter, I'm trying to see if the people that did the first mapping have any of the old datalogs around which would tell me how much boost it was running last year.

In July last year it ran 275bhp, this year it ran 234 before mapping and 274 after mapping again so there's obviously something amiss which I need to sort.

[GreenV8S]

Butter Face said:

should do 13-14psi (as I've been told)

More boost isn't always better. The goal is power, not boost. Is it achieving the expected power from that blower gearing?

You can think of manifold pressure is a measure of back pressure from the engine. A lower manifold pressure might mean it's receiving less air from the charger, but could equally mean that the engine is breathing better or the incoming air is cooler.

[stevieturbo]

Butter Face said:

To answer the questions as well as I can:

Because I have been told so, the C30-94 with a 110mm pulley should do 13-14psi (as I've been told) but there is so much conflicting information online that it's virtually impossible to know what the correct information is.

I have a friend with the same top mounted C30-94, 110mm pulley like mine, and his is doing 12psi and 383bhp. He has a front mount like I do but has a full manifold/decat/3inch exhaust whereas I have the standard manifold/exhaust but with a decat.

I have checked for leaks and none found, but never rule it out. Belt slip doesn't seem to be an issue, standard tensioner is normally fine but I do actually have a manual one to replace it.

Only information I have is the technical sheet from rotrex here - https://www.google.com/url?sa=t&rct=j&q=&a... if that helps!

I try an understand as I can, but this is all confusing the hell out of me!

So his is an identical engine , same pulley sizes and his makes 13psi vs yours at only 7-8 or so ?

Again, a graph of rpm vs boost would help ( even better from both cars )

Belt slip could always be an issue, and I would always say use a good strong spring tensioner as opposed to a fixed manual. Although I'd expect a small blower like that not to be too hard on belts. But same principals apply.

And has yours ever made the boost you think it should ? How are you measuring boost, and is this proven to be accurate ?

[Butter Face]

Thought I’d update this in case anyone needs it in the future, I now have a 100mm pulley on my C30-94 and it makes 1bar of boost at around 7500rpm (can’t remember exactly) and the car now makes 357bhp which is a nice upgrade!