GTM Libra B18C
Discussion
Just thought I'd post a little update
Still plodding on, date of the 4th march for paint looming but it's getting there. Have done a number of crazing repairs.. basically this consists of grinding any cracks out of the gel coat and filling back in with short strand fibre filler, flat back then finish with very fine filler ready for primer.
Seem to start a panel then find another, then another etc etc. But it needs doing right, it adds strength to the stressed areas where crazing has occurred and means it can't come back through and ruin the paint.
Readers of a nervous disposition look away now
Basically got patches like that all over the car. Well, clams and a little on the doors, not the tub.
Think it'll probably be a month or so yet till I get anything from Z cars too but there's no major rush...
One idea I have been toying with is turboing it, there's an abosulute mass of info out there regarding turbo B series Hondas and I'm quite confident it can be done reasonably cheap and with a good safe tune be able to churn out a reliable 300ish hp.
I was always tempted to do something mad with it once the paint is done and it's handling right and TBH was favouring an NA build but it just seems like a bottomless pit of spending, for what, 250hp? Plus it's the torque that will really be impressive.
There's plenty of guys running low ish boost on fairly high compression, if I pop the 11:1 type R pistons and rods out I can easily fit B18C4 pistons on H beam rods without even removing the engine, that will net 9.8:1. The main difficulty will be fitting it all in such a tiny space...
I've thought about it a lot over the last few days and just found these turbo flange to V band adapters
I think that with 2 of these, I.e one on the manifold and one on the turbo, I can basically just pipe between them and mount the turbo wherever I want it... obviously the shorter the better. It would be a quick and easy way to replicate a sidewinder style exhaust where the turbo sits more over the box where there's more space. V clamps allow everything to be turned too which helps on something custom like this. Then wrap all the tubing and make some support brackets. Bit of a brain fart at the moment but I think it's do able, otherwise there's simply not enough space infront
Of the engine.
This is the normal kind of setup
Maybe a top mount would be better to keep some room below for the downpipe etc.
Possibly something like this bolted to the manifold either on a top or bottom mount manifold with the straight v band adapter on the turbo. This should put the turbine facing upwards which would even make it easier to plumb in but would mean I couldn't use an off the shelf down pipe. But there's going to have to be a compromise somewhere.
Anyone have any ideas?
Theres basically some room around the gearbox and plenty of room above the engine, just not much in front
Still plodding on, date of the 4th march for paint looming but it's getting there. Have done a number of crazing repairs.. basically this consists of grinding any cracks out of the gel coat and filling back in with short strand fibre filler, flat back then finish with very fine filler ready for primer.
Seem to start a panel then find another, then another etc etc. But it needs doing right, it adds strength to the stressed areas where crazing has occurred and means it can't come back through and ruin the paint.
Readers of a nervous disposition look away now
Basically got patches like that all over the car. Well, clams and a little on the doors, not the tub.
Think it'll probably be a month or so yet till I get anything from Z cars too but there's no major rush...
One idea I have been toying with is turboing it, there's an abosulute mass of info out there regarding turbo B series Hondas and I'm quite confident it can be done reasonably cheap and with a good safe tune be able to churn out a reliable 300ish hp.
I was always tempted to do something mad with it once the paint is done and it's handling right and TBH was favouring an NA build but it just seems like a bottomless pit of spending, for what, 250hp? Plus it's the torque that will really be impressive.
There's plenty of guys running low ish boost on fairly high compression, if I pop the 11:1 type R pistons and rods out I can easily fit B18C4 pistons on H beam rods without even removing the engine, that will net 9.8:1. The main difficulty will be fitting it all in such a tiny space...
I've thought about it a lot over the last few days and just found these turbo flange to V band adapters
I think that with 2 of these, I.e one on the manifold and one on the turbo, I can basically just pipe between them and mount the turbo wherever I want it... obviously the shorter the better. It would be a quick and easy way to replicate a sidewinder style exhaust where the turbo sits more over the box where there's more space. V clamps allow everything to be turned too which helps on something custom like this. Then wrap all the tubing and make some support brackets. Bit of a brain fart at the moment but I think it's do able, otherwise there's simply not enough space infront
Of the engine.
This is the normal kind of setup
Maybe a top mount would be better to keep some room below for the downpipe etc.
Possibly something like this bolted to the manifold either on a top or bottom mount manifold with the straight v band adapter on the turbo. This should put the turbine facing upwards which would even make it easier to plumb in but would mean I couldn't use an off the shelf down pipe. But there's going to have to be a compromise somewhere.
Anyone have any ideas?
Theres basically some room around the gearbox and plenty of room above the engine, just not much in front
Edited by Yazza54 on Thursday 16th February 07:41
Hmm I tend to agree, but the fact remains I want to do something with it. I was leaning towards possibly a rotrex but that's even worse for space, dearer and I don't like the complication of the extra belt.
I've looked into NA tuning and to make any meaningful gains it would probably mean sleeving the block out to 85mm so it's close to 2 litres, forged pistons, rods, and all new valvetrain, inlet manifold etc etc and after all that it might make say 250hp. Doesn't seem worth it. There's a lot of people running high ish comp/low boost turbos now which are supposedly nice and tractable. With a good tune they can make a safe 300hp and have more low down pull on 10:1 as opposed to let's say more boost on 9:1.
I've looked into NA tuning and to make any meaningful gains it would probably mean sleeving the block out to 85mm so it's close to 2 litres, forged pistons, rods, and all new valvetrain, inlet manifold etc etc and after all that it might make say 250hp. Doesn't seem worth it. There's a lot of people running high ish comp/low boost turbos now which are supposedly nice and tractable. With a good tune they can make a safe 300hp and have more low down pull on 10:1 as opposed to let's say more boost on 9:1.
Sway said:
I always struggled with the idea of big power in the Libra - following Bertram's (?) build with the VAG turbo and DSG box I always thought that it was a tad daft.
Not big gains, but how about irtbs? Just the noise and crisp throttle response would give the feeling of a huge improvement, regardless of actual dyno figures?
Surprised at the amount of crazing on the clams, mine had absolutely none of that - wonder if it's an age thing (my tub was one of the last GTM ones, the clamshells were from Potenza after they bought GTM)?
I don't want to speak ill of the previous owner, but it's blatantly obvious to me that the car wasn't very well looked after. I've heard stories of the GRP being better on the original cars but a lot of the repairs I've had to do were more down to lets say user error from what I can tell... Not big gains, but how about irtbs? Just the noise and crisp throttle response would give the feeling of a huge improvement, regardless of actual dyno figures?
Surprised at the amount of crazing on the clams, mine had absolutely none of that - wonder if it's an age thing (my tub was one of the last GTM ones, the clamshells were from Potenza after they bought GTM)?
I agree regarding the idea of a big power Libra, however, neither you or me have ever owned a Z cars converted Libra.... I'm 100% certain that in standard form the car couldn't handle it, but with the Z cars kit it should be a different kettle of fish. After all there is someone running a K20 Rotrex'd Libra at the moment with 350hp and he says it's a great package.
Bertram's car was very well done but also quite complicated especially with the DSG, extra radiators for charge coolers etc etc. I would look to keep things as simple as possible.
dom9 said:
That's very true. When you can (hopefully) carry more speed everywhere with the new rear suspension set up then you may feel differently.
I am guessing you have 200+bhp with a nice exhaust, filter and remap on the B18C, which does sound 'a lot' on a car that small and light.
I'd tend to agree that an LP turbo might give you a little 'more' without losing too much character but it would be a shame if any 'zing' was lost.
It is a lot in terms of power to weight, but nowadays every baseball cap turning kid is blatting round in a 300hp golf, civic or insert other.. cars are just a lot more powerful nowadays, although a big player in this is because cars have also become much more bloated!!I am guessing you have 200+bhp with a nice exhaust, filter and remap on the B18C, which does sound 'a lot' on a car that small and light.
I'd tend to agree that an LP turbo might give you a little 'more' without losing too much character but it would be a shame if any 'zing' was lost.
We'll see... with regards to zing it'll still rev to 8500 whether it's got a snail attached to it or not
Ant_ITR said:
if you were to go turbo you would be better selling the b18c6 and getting a b18c4 found in the mb6 civic, they are a lower comp as standard and take better to turbo conversions, the b18c6 you have now would sell for around £2kish and you should be able to pick up a c4 for around £500
I know but there's something nice about having a unit you know works. I can easily drop a set of C4 pistons in anyway. Plus it remains a type R with its better balanced crank and type R head/cams. I'm not looking to do a major transplant, if I do anything at all. TBH initially I was just thinking of cams and map, then I thought that wouldn't make much difference so started thinking about sleeving the block and now here we are talking about bloody turbos
Ant_ITR said:
Yazza54 said:
Ant_ITR said:
if you were to go turbo you would be better selling the b18c6 and getting a b18c4 found in the mb6 civic, they are a lower comp as standard and take better to turbo conversions, the b18c6 you have now would sell for around £2kish and you should be able to pick up a c4 for around £500
I know but there's something nice about having a unit you know works. I can easily drop a set of C4 pistons in anyway. Plus it remains a type R with its better balanced crank and type R head/cams. I'm not looking to do a major transplant, if I do anything at all. TBH initially I was just thinking of cams and map, then I thought that wouldn't make much difference so started thinking about sleeving the block and now here we are talking about bloody turbos
It already has a 2.5 inch system throughout and 4-2-1 PLM manifold, with a straight through silencer and currently decatted. I've been thinking of buying a S300 so I can get the most out of what I have and I've always got it there for the future flexibility too.
Another idea I had was a B20 Block with B18 rods and crank, I think that makes around 1932cc, kinda like a poor mans way of making a 84mm B18c.. I know the sleeves are reportedly weaker in a B20 but that only becomes apparent under boost or detonation from what I gather. Plus using a B18 crank and rods at least retains a slightly better rod/stroke ratio.
I'd love to rotrex it but the problem remains with lack of space.
Will park all these ideas until the car is painted and Z cars kit is on...
I'd love to rotrex it but the problem remains with lack of space.
Will park all these ideas until the car is painted and Z cars kit is on...
Edited by Yazza54 on Friday 17th February 10:32
Little update, prepping the car for paint has unfortunately been more time consuming than I'd hoped... I'm now dropping the car off on the 18th, not this Saturday (4th). Really wanted to hit the date agreed but it was just stressing me out too much and not something that should be rushed.
In other news I managed to pick up some nice H beam rods complete with 9mm ARP bolts and a full new ARP head stud kit for about half price off someone who collected the bits and had to have a change of plan... just going to keep picking up bits as I go, but the main thing is I'm still on the look out for a C30-94 Rotrex.
Had some correspondence from Z Cars too, sounds like the kit is about a month away from manufacture.
In other news I managed to pick up some nice H beam rods complete with 9mm ARP bolts and a full new ARP head stud kit for about half price off someone who collected the bits and had to have a change of plan... just going to keep picking up bits as I go, but the main thing is I'm still on the look out for a C30-94 Rotrex.
Had some correspondence from Z Cars too, sounds like the kit is about a month away from manufacture.
So I've been doing some digging
I'm a sucker for a challenge and none of the off the shelf rotrex kits are going to fit this car, as they all fit on the exhaust side where I have no space. The immediate problems I've faced while designing this in my head are the availability of 4 rib belts, and to run it with a single serpentine belt I will need a double backed belt so I can run the rotrex off the back of the belt, otherwise it'll be spinning backwards with the engine.
There are not many 4 rib double sided belts on the market at all, furthermore I think a 4 rib belt is pretty poor for a supercharger. This got me thinking, is a 6 rib pulley available???
The answer is/was no... however.. while searching I stumbled across a Honda D series forum, where a few people have built D16 strokers with a D17 crank. What they found was that the D17 crank snout was much bigger so they either had to use the D17 pulley/oil pump, or turn down the snout to use the original bits. Then some further searching on this topic revealed that some people had used B16/B18 crank pulleys on the D17 crank.... therefore a bit of reverse engineering tells me a D17 pulley should fit a B18C crank... and... it's a 6 rib pulley. Bingo!
I've also found out that the alternator pulley is the same ID too... so I can convert to 6 rib for peanuts and already have the bits on the way to check offsets etc. but Any minor difference in offset should be easy to put right, if needed.
Now as a lot of OEM serpentine belt setups utilise a 6 rib double sided belt, this means there's a myriad of belt lengths available off the shelf.
I'm just going to keep collecting bits but as far as I'm concerned the hard bit of designing it out is already done now and I can run a better belt than the other kits and run the rotrex above the alternator where I have some space.
Little sketch, obviously a tensioner needs to go somewhere too, maybe near the alternator
I'm a sucker for a challenge and none of the off the shelf rotrex kits are going to fit this car, as they all fit on the exhaust side where I have no space. The immediate problems I've faced while designing this in my head are the availability of 4 rib belts, and to run it with a single serpentine belt I will need a double backed belt so I can run the rotrex off the back of the belt, otherwise it'll be spinning backwards with the engine.
There are not many 4 rib double sided belts on the market at all, furthermore I think a 4 rib belt is pretty poor for a supercharger. This got me thinking, is a 6 rib pulley available???
The answer is/was no... however.. while searching I stumbled across a Honda D series forum, where a few people have built D16 strokers with a D17 crank. What they found was that the D17 crank snout was much bigger so they either had to use the D17 pulley/oil pump, or turn down the snout to use the original bits. Then some further searching on this topic revealed that some people had used B16/B18 crank pulleys on the D17 crank.... therefore a bit of reverse engineering tells me a D17 pulley should fit a B18C crank... and... it's a 6 rib pulley. Bingo!
I've also found out that the alternator pulley is the same ID too... so I can convert to 6 rib for peanuts and already have the bits on the way to check offsets etc. but Any minor difference in offset should be easy to put right, if needed.
Now as a lot of OEM serpentine belt setups utilise a 6 rib double sided belt, this means there's a myriad of belt lengths available off the shelf.
I'm just going to keep collecting bits but as far as I'm concerned the hard bit of designing it out is already done now and I can run a better belt than the other kits and run the rotrex above the alternator where I have some space.
Little sketch, obviously a tensioner needs to go somewhere too, maybe near the alternator
Edited by Yazza54 on Monday 6th March 16:56
I agree, it's not accurate at all just shows the general layout. I could do with taking some measurements so I can CAD it up. For now I at least know that it's a go-er as before figuring these details out it wasn't looking do able without lots of custom components and ££££££.
I think the top two jockey wheels could be slightly higher and closer together too for more wrap around the charger pulley.
This is how the kraftwerks kit is
I think the top two jockey wheels could be slightly higher and closer together too for more wrap around the charger pulley.
This is how the kraftwerks kit is
Edited by Yazza54 on Tuesday 7th March 07:06
Slightly better sketch, showing the tensioner and better positioning of jockey wheels for more wrap. Having had a look at other belt layouts of OEM supercharged and retrofits I don't think the alternator needs any more wrap than this, some even have less. It will be well tensioned and 50% wider belt than standard so I don't foresee an issue.
Sway said:
Awesome. Proper fabrication!
Seems I'd missed a few of the recent updates - I don't know how applicable it is but the Kraftwerks rotrex kits for the mx5 were plagued with problems - mounting plates that flexed like mad, alignment issues, all sorts!
I do agree however, I can't think of many things better than a rotrex for this application.
Yeah looking forward to getting it thrown on then I'll take it somewhere for a full set up. Should get the car back from the paint shop next week too. Seems I'd missed a few of the recent updates - I don't know how applicable it is but the Kraftwerks rotrex kits for the mx5 were plagued with problems - mounting plates that flexed like mad, alignment issues, all sorts!
I do agree however, I can't think of many things better than a rotrex for this application.
Engine wise I'm thinking I might just keep it NA after all. But we'll see... it's a bloody brilliant engine as it is.
Just had a chat with Chris at Z cars, they have made some minor adjustments to the kit and it will have wider track built in, as many people were running the original kit at its widest possible adjustment. This is good news for me as there will be more clearance for my engine and box as the B18C is longer than the Rover K. They are also designing replacement top wishbones that are adjustable as it is near impossible to get the geometry right on a standard libra. The factory suggested you shim the wishbone mounts to achieve this which is just a terrible and time consuming method. Just waiting on a price- hopefully not too eye watering..!
Finally got the car back painted. Can't say it's the best job in the world but it looks a damn lot better... I think with me knowing where all the bad bits were etc. I'm always going to be more critical than most people would be. It looks very striking now. Get my new lights and plates fitted and then I probably won't be touching the car until the Z cars kit is on.
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
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