GTM Libra B18C
Discussion
Ha! I had my first proper run out in the car for a day and had a number of observations. Basically as great as the engine is it really lacks torque. It goes well when it's revving it's nuts off but that's just not what I want on the road. The other observation is that because of the 4.78 diff it's revving it's crackers off on the motorway too and my ears were near bleeding just cruising at 70.... it's just too much.
So I came away thinking that the car would be a hell of a lot better with more grunt and if I had more grunt I could change the diff so it wasn't always buzzing so bloody much.
Very early days but we'll see how I get on, I just came across this brand new vortech charger in the US for about a quarter of it's value and after doing all the research in the end it happened to be the one I'd settled on, if I ever decided to supercharge it - then hey presto one appeared!
It's a counter clockwise unit so no myriad of idler pulleys needed to make it run the correct way like I'd have to do if I used a rotrex which are clockwise only (my Honda engine spins backwards), it's also completely self contained, runs on its own fancy ATF oil so doesn't have to be plumbed into the engine oiling or have its own oil cooler and reservoir like a rotrex. So whilst it's a big unit it's actually quite neat.
I've got a few ideas with regards to set up but for the time being I just need to make some mounts and get it all aligned which I suspect won't be as easy as it sounds.
What I would like to do, and I know it has been done before is use some sort of boost control or bleed off with it. The problem with centrifugal superchargers is that you can only spin them so fast and most people pulley them up to produce whatever boost you want at max engine RPM.
So let's say this supercharger can spin up to 52000 but at around 42000 it'll make 9-10psi which is all I really want... most people would just pulley them up to hit 42000 at max engine revs, in my case 8600rpm.
What I'm toying with is making it hit it's maximum 52000rpm impeller speed at 8600rpm, but bleeding pressure off, meaning that at peak I'm still only going to be at 9-10psi, but it will make more mid range as it'll hit that plateau of boost much sooner, approx 1750rpm sooner. From reading into it this isn't something recommended for screw/roots blowers but it's perfectly do-able on a centrifugal unit and whilst people always purvey the idea of keeping it simple I don't honestly think it's going to be all that complicated to set up. After all it's not really any different to boost controlling a turbo set up, and like a turbo it will reach its maximum boost sooner (granted not as soon as a turbo) than if I just pulley'd it to run at say 75% of its speed, but unlike a turbo it shouldn't have any lag. It won't be forever bleeding off boost either, probably anything over 7000rpm it will be.
Anyway, we'll see. Plenty to get on with... still haven't even got the Z cars kit on the frigging thing.
So I came away thinking that the car would be a hell of a lot better with more grunt and if I had more grunt I could change the diff so it wasn't always buzzing so bloody much.
Very early days but we'll see how I get on, I just came across this brand new vortech charger in the US for about a quarter of it's value and after doing all the research in the end it happened to be the one I'd settled on, if I ever decided to supercharge it - then hey presto one appeared!
It's a counter clockwise unit so no myriad of idler pulleys needed to make it run the correct way like I'd have to do if I used a rotrex which are clockwise only (my Honda engine spins backwards), it's also completely self contained, runs on its own fancy ATF oil so doesn't have to be plumbed into the engine oiling or have its own oil cooler and reservoir like a rotrex. So whilst it's a big unit it's actually quite neat.
I've got a few ideas with regards to set up but for the time being I just need to make some mounts and get it all aligned which I suspect won't be as easy as it sounds.
What I would like to do, and I know it has been done before is use some sort of boost control or bleed off with it. The problem with centrifugal superchargers is that you can only spin them so fast and most people pulley them up to produce whatever boost you want at max engine RPM.
So let's say this supercharger can spin up to 52000 but at around 42000 it'll make 9-10psi which is all I really want... most people would just pulley them up to hit 42000 at max engine revs, in my case 8600rpm.
What I'm toying with is making it hit it's maximum 52000rpm impeller speed at 8600rpm, but bleeding pressure off, meaning that at peak I'm still only going to be at 9-10psi, but it will make more mid range as it'll hit that plateau of boost much sooner, approx 1750rpm sooner. From reading into it this isn't something recommended for screw/roots blowers but it's perfectly do-able on a centrifugal unit and whilst people always purvey the idea of keeping it simple I don't honestly think it's going to be all that complicated to set up. After all it's not really any different to boost controlling a turbo set up, and like a turbo it will reach its maximum boost sooner (granted not as soon as a turbo) than if I just pulley'd it to run at say 75% of its speed, but unlike a turbo it shouldn't have any lag. It won't be forever bleeding off boost either, probably anything over 7000rpm it will be.
Anyway, we'll see. Plenty to get on with... still haven't even got the Z cars kit on the frigging thing.
Edited by Yazza54 on Friday 29th September 06:08
rdodger said:
Ryan
Would it not be more straightforward to fit a restrictor on the outlet as they do with Rotrex?
Seems to me that would be less accurate, probably less efficient and would need a handful of them making to try on a dyno before figuring out which is the one I need. I think the better solution is to run the supercharger as its intended to be run and just bleed any excess off. Plus there's always the option to just up it either at the push of a button or manually depending how complex the system is. A restrictor is a bit of a frig really and for the dyno/development time it would take to get the boost level I wanted that would cancel out any savings money wise, after all this is going to be a completely custom build so there is no off the shelf solution.... and after all that messing about getting restrictors made and testing them, it still won't be as good as a controlled system.Would it not be more straightforward to fit a restrictor on the outlet as they do with Rotrex?
I don't think it necessarily has to be to over complicated, the one I've seen done in the USA had a BOV after the intercooler and the wastegate before the intercooler, pretty sure that just had say a 9psi spring or whatever he wanted to run in it and hey presto, boost builds sooner and never exceeds that level.
Edited by Yazza54 on Friday 29th September 11:36
It is NA, I never started to do the work to supercharge it. Basically to cut a long story short I've realised that I'm not really getting any enjoyment out of what I'm doing and I miss racing. So need the money and the space back. The car is perfectly useable as is. Z cars kit can either go with it or I'll get my money back via Z cars themselves.
Yazza54 said:
It is NA, I never started to do the work to supercharge it. Basically to cut a long story short I've realised that I'm not really getting any enjoyment out of what I'm doing and I miss racing. So need the money and the space back. The car is perfectly useable as is. Z cars kit can either go with it or I'll get my money back via Z cars themselves.
Any idea where you might go from here?Yazza54 said:
Someone's emailed me about the car called poppopbang. but when I replied it came up as undeliverable, can you message me again and leave a number or another email address please.
poppopbangbang is his username, you've missed off a bang...this is the company he works for, might be a contact number/email address there https://www.tour-de-force.co.uk/
Robmarriott said:
poppopbangbang is his username, you've missed off a bang...
this is the company he works for, might be a contact number/email address there https://www.tour-de-force.co.uk/
Cheers, emailed but no response as yet this is the company he works for, might be a contact number/email address there https://www.tour-de-force.co.uk/
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