Rover 200 BRM - 1.8 K-Series turbo project
Discussion
I have removed the Ferriday copper plate and machined the Wössner 9:1 pistons to remove the thin ledge in the valve pockets.
I have found as expected that despite increased CR, knock resistance increased substantially at all rev ranges. I was able to advance timing and gain power almost everywhere.
This is just to confirm what max_torque said. Flat side walls, poor squish and quench are not good for knock resistance. There is still a 1.6mm gap between the head and the piston crown in the squish area, but this is better that 2.6mm. I cannot go lower than that with these pistons as they do not protrude the cylinder at TDC.
After a brief drive with 1 bar in this new configuration and checking my heat shields and other installations I have found that I have a hard time managing the heat running 1 bar of boost. My HJS Motorsport 200 cell cat converter died and turned white, my wheel arch liners started to melt and a piece of the cam belt cover was melted away.
I decided to reduce boost to a ore sensible 0.75bar at 7500 rpm (0.7 bar at 7000). Power is now more consistent on track as intake air temps are also now more manageable. a Rotrex C30-94 spinning to 100000 rpm and a pressure ratio of 2.5 create a fair bit of heat in the air it supplies.
the engine itself copes fine with 1 bar of boost it seems.
I have since competed two trackways with the new configuration (machined JDM Dyno Wössner pistons, removed copper plate, 0.75bar) without any issues.
All 4 modified pistons back in the engine.
Piston tops after head removal. You can clearly see where the water/methanol ix from the direct port injection nozzles reduced carbon build up. it is pretty uniform and on both intake and exhaust side. this shows that the spray passes both the intake valve's rear and front. with the nozzles on top of the runners in the past did did not happen.
in the engine before machining. they all look the same, so I just show one.
one of the pistons I machined with a Dremel by hand. Not a professional std, but it worked OK for me. this is the only close up I took and it is the worst looking one. It was deburred before installation.
Rear of the piston. you see there is no yellow discolouration indicating excess piston crown temperatures.
Cylinder head after removal. looks all good to me.
I have found as expected that despite increased CR, knock resistance increased substantially at all rev ranges. I was able to advance timing and gain power almost everywhere.
This is just to confirm what max_torque said. Flat side walls, poor squish and quench are not good for knock resistance. There is still a 1.6mm gap between the head and the piston crown in the squish area, but this is better that 2.6mm. I cannot go lower than that with these pistons as they do not protrude the cylinder at TDC.
After a brief drive with 1 bar in this new configuration and checking my heat shields and other installations I have found that I have a hard time managing the heat running 1 bar of boost. My HJS Motorsport 200 cell cat converter died and turned white, my wheel arch liners started to melt and a piece of the cam belt cover was melted away.
I decided to reduce boost to a ore sensible 0.75bar at 7500 rpm (0.7 bar at 7000). Power is now more consistent on track as intake air temps are also now more manageable. a Rotrex C30-94 spinning to 100000 rpm and a pressure ratio of 2.5 create a fair bit of heat in the air it supplies.
the engine itself copes fine with 1 bar of boost it seems.
I have since competed two trackways with the new configuration (machined JDM Dyno Wössner pistons, removed copper plate, 0.75bar) without any issues.
All 4 modified pistons back in the engine.
Piston tops after head removal. You can clearly see where the water/methanol ix from the direct port injection nozzles reduced carbon build up. it is pretty uniform and on both intake and exhaust side. this shows that the spray passes both the intake valve's rear and front. with the nozzles on top of the runners in the past did did not happen.
in the engine before machining. they all look the same, so I just show one.
one of the pistons I machined with a Dremel by hand. Not a professional std, but it worked OK for me. this is the only close up I took and it is the worst looking one. It was deburred before installation.
Rear of the piston. you see there is no yellow discolouration indicating excess piston crown temperatures.
Cylinder head after removal. looks all good to me.
Edited by Ive on Sunday 14th August 13:55
Edited by Ive on Sunday 14th August 13:57
Edited by Ive on Sunday 14th August 14:06
Max_Torque said:
Run with the long plugs, but take the last few threads off the plugs and make sure you remove the last thread in the head! High CR on turbo's is not, in itself an issue, as long as you run sensible boost pressures at low/mid rpm and have it nicely mapped. Full house WRC engines run just under 12:1 on a 34mm restricted (ie high internal EGR) turbo running 3 bar of boost! (but they have had a LOT of combustion development)
as you are just 2wd, there is no point throwing massive boost at the thing at low rpm (say 3krpm) because you just won't be able to put the torque on the ground anyway. And when you get up the gear box and are going fast, then you'll also be up the rev range and at peak power, where the high static CR means you can run low boost and still make good power. Added to which, the ratio of N/A to Boosted torque will be more favourable, reducing lag and making the car drive really nicely (ie you should be able to accurately modulate torque across the full load threshold).
I did exactly the same thing for the engine in my tarmac rally car, optimising the engine for high rpm power rather than low rpm torque (because i'm 2wd too, unlike the 4wd WRC cars that go faster the more torque you give them, whereas my car just goes sideways and wrecks the rear tyres ;-) ) I run water injection in the high boost "stage" mode, but i'm running 2.6bar gauge at 7800rpm on a CR in the high 11s
That make a lot of sense. Thanks for taking the time to write that! I've heard of some high compression turbo builds but could never find much detail about them. as you are just 2wd, there is no point throwing massive boost at the thing at low rpm (say 3krpm) because you just won't be able to put the torque on the ground anyway. And when you get up the gear box and are going fast, then you'll also be up the rev range and at peak power, where the high static CR means you can run low boost and still make good power. Added to which, the ratio of N/A to Boosted torque will be more favourable, reducing lag and making the car drive really nicely (ie you should be able to accurately modulate torque across the full load threshold).
I did exactly the same thing for the engine in my tarmac rally car, optimising the engine for high rpm power rather than low rpm torque (because i'm 2wd too, unlike the 4wd WRC cars that go faster the more torque you give them, whereas my car just goes sideways and wrecks the rear tyres ;-) ) I run water injection in the high boost "stage" mode, but i'm running 2.6bar gauge at 7800rpm on a CR in the high 11s
I've been fettling the good head and the most I can get out of it is 2.5cc. That'll lower CR to about 11:1. The squish clearance will be about 1.5mm.
I've been offered a set of 2mm shorter rods but I'm just not prepared to do that. Likewise with using a head shim or thicker gasket.
To be honest, I think I'm just going to build it at 11:1 and run at 5psi boost to start with and see what happens. Need to find a good mapper!
Ive said:
I have removed the Ferriday copper plate and machined the Wössner 9:1 pistons to remove the thin ledge in the valve pockets.
I have found as expected that despite increased CR, knock resistance increased substantially at all rev ranges. I was able to advance timing and gain power almost everywhere.
Looking good! Glad it's got you the result you were hoping for. I only wish I'd known about this before... I have found as expected that despite increased CR, knock resistance increased substantially at all rev ranges. I was able to advance timing and gain power almost everywhere.
What exhaust manifold do you run? I see you have the thermal intake gaskets (ferriday?) Do you run a thermal exhaust plate as well?
The squish and mixture motion thing has been done and explained already on P14, we're just going round in circles here.
How the heck did you manage to mistakenly order pistons with such a high CR?!
Whilst I don't disagree with the high CR argument, we are talking about a novice build and tune here, not some multi million pound WRC budget and equipment designed to shave a tenth of a second off a rally stage.
The higher the CR, the closer you run on a knife edge with extreme det one one side and there is very little margin for error. With 8 or 9:1 you end up with a much safer motor able to run on 95 supermarket juice without any worry.
I'm not against high CR engines at all, but the advantages are so minor and the danger factor so high with a home build like this i'd avoid it or proceed with extreme caution.
How the heck did you manage to mistakenly order pistons with such a high CR?!
Whilst I don't disagree with the high CR argument, we are talking about a novice build and tune here, not some multi million pound WRC budget and equipment designed to shave a tenth of a second off a rally stage.
The higher the CR, the closer you run on a knife edge with extreme det one one side and there is very little margin for error. With 8 or 9:1 you end up with a much safer motor able to run on 95 supermarket juice without any worry.
I'm not against high CR engines at all, but the advantages are so minor and the danger factor so high with a home build like this i'd avoid it or proceed with extreme caution.
I only run the intake insulation gasket . The manifold is a solid (no flexi) EBD 4-2-1. The exhaust is mounted with two std Rover K exhaust gaskets. This was a advice from Roger Fabry of Sabreheads. The flanges of the manifolds are rarely flat after seeing some heat. Two gaskets as a sandwich create a reliable seal. I have done this a few times and never had issues. I even reused them a few times.
11:1 CR together with say 5-7 PSI boost is mappable. Past 5500-6000 it can take more as volumetric efficiency drops.
I have done this in the past due to high CR pistons. Good low down torque, but the mid and top range is severly knock limited. This led to a rising power curve, but slightly dropping torque curve. while it is fast, it does not feel sporty. you tend to short shift. Wtih the low CR build, power and torque rise with rpm resulting in a engine you actually like to rev high. it pulls harder as revs rise.
The more octane or water/meth you throw at such a high CR engine, the more power you extract.
Can you post your volume numbers you used to come up with the CR, just to be sure.
I can see this happening as the sweeped volume increases a fair bit going to 82mm bore from 80mm while the head volume stays the same. This is what is causing the issues. When I had my big bore 565cc RG500 engine build by Marc Dent it involved machining the combustion chambers to restore a sensible CR.
12:1 is no fun to map for FI, especially if you do not have knock control in the car.
You may extend the combustion chamber at the sides to gain volume. But still as mentioned before, 7cc is a lot of material.
Without you and hearing about my old pistons Wössner 12:1 pistons starting to have the same issue, we would not know.
I sold hem on to be used in a NA buildm but upon closer inspection one of the valve pockets showed the same issues.
I refunded the money and used them to practise the piston modification.
11:1 CR together with say 5-7 PSI boost is mappable. Past 5500-6000 it can take more as volumetric efficiency drops.
I have done this in the past due to high CR pistons. Good low down torque, but the mid and top range is severly knock limited. This led to a rising power curve, but slightly dropping torque curve. while it is fast, it does not feel sporty. you tend to short shift. Wtih the low CR build, power and torque rise with rpm resulting in a engine you actually like to rev high. it pulls harder as revs rise.
The more octane or water/meth you throw at such a high CR engine, the more power you extract.
Can you post your volume numbers you used to come up with the CR, just to be sure.
I can see this happening as the sweeped volume increases a fair bit going to 82mm bore from 80mm while the head volume stays the same. This is what is causing the issues. When I had my big bore 565cc RG500 engine build by Marc Dent it involved machining the combustion chambers to restore a sensible CR.
12:1 is no fun to map for FI, especially if you do not have knock control in the car.
You may extend the combustion chamber at the sides to gain volume. But still as mentioned before, 7cc is a lot of material.
Without you and hearing about my old pistons Wössner 12:1 pistons starting to have the same issue, we would not know.
I sold hem on to be used in a NA buildm but upon closer inspection one of the valve pockets showed the same issues.
I refunded the money and used them to practise the piston modification.
Edited by Ive on Sunday 14th August 19:30
Edited by Ive on Sunday 14th August 19:47
I only run the intake insulation gasket . The manifold is a solid (no flexi) EBD 4-2-1. The exhaust is mounted with two std Rover K exhaust gaskets. This was a advice from Roger Fabry of Sabreheads. The flanges of the manifolds are rarely flat after seeing some heat. Two gaskets as a sandwich create a reliable seal. I have done this a few times and never had issues. I even reused them a few times.
11:1 CR together with say 5-7 PSI boost is mappable. Past 5500-6000 it can take more as volumetric efficiency drops.
I have done this in the past due to high CR pistons. Good low down torque, but the mid and top range is severly knock limited. This led to a rising power curve, but slightly dropping torque curve. while it is fast, it does not feel sporty. you tend to short shift. Wtih the low CR build, power and torque rise with rpm resulting in a engine you actually like to rev high. it pulls harder as revs rise.
The more octane or water/meth you throw at such a high CR engine, the more power you extract.
Can you post your volume numbers you used to come up with the CR, just to be sure.
I can see this happening as the sweeped volume increases a fair bit going to 82mm bore from 80mm while the head volume stays the same. This is what is causing the issues. When I had my big bore 565cc RG500 engine build by Marc Dent it involved machining the combustion chambers to restore a sensible CR.
12:1 is no fun to map for FI, especially if you do not have knock control in the car.
You may extend the combustion chamber at the sides to gain volume. But still as mentioned before, 7cc is a lot of material.
Without you and hearing about my old pistons Wössner 12:1 pistons starting to have the same issue, we would not know.
I sold hem on to be used in a NA buildm but upon closer inspection one of the valve pockets showed the same issues.
I refunded the money and used them to practise the piston modification.
11:1 CR together with say 5-7 PSI boost is mappable. Past 5500-6000 it can take more as volumetric efficiency drops.
I have done this in the past due to high CR pistons. Good low down torque, but the mid and top range is severly knock limited. This led to a rising power curve, but slightly dropping torque curve. while it is fast, it does not feel sporty. you tend to short shift. Wtih the low CR build, power and torque rise with rpm resulting in a engine you actually like to rev high. it pulls harder as revs rise.
The more octane or water/meth you throw at such a high CR engine, the more power you extract.
Can you post your volume numbers you used to come up with the CR, just to be sure.
I can see this happening as the sweeped volume increases a fair bit going to 82mm bore from 80mm while the head volume stays the same. This is what is causing the issues. When I had my big bore 565cc RG500 engine build by Marc Dent it involved machining the combustion chambers to restore a sensible CR.
12:1 is no fun to map for FI, especially if you do not have knock control in the car.
You may extend the combustion chamber at the sides to gain volume. But still as mentioned before, 7cc is a lot of material.
Without you and hearing about my old pistons Wössner 12:1 pistons starting to have the same issue, we would not know.
I sold hem on to be used in a NA buildm but upon closer inspection one of the valve pockets showed the same issues.
I refunded the money and used them to practise the piston modification.
Edited by Ive on Sunday 14th August 19:30
Edited by Ive on Sunday 14th August 20:32
Might as well bite the bullet and get new pistons as squish clearance AND compression ratio seem to be waaaay off. Any chance of a refund/swap?
Decompression plates and thick gaskets are a vicious circle so avoid.
Max might be able to make 12:1 CR work but he's got access to more state of the equipment and talent than the likes of us. And he runs 102RON and water injection.
High CR might be okay if you need to protect the gearbox, otherwise it depends on the power delivery you want. Personally I'd go lower to give the freedom to choose high boost should I want it, but that's just me.
Do you want a smooth build up or a massive thump in the back?
Decompression plates and thick gaskets are a vicious circle so avoid.
Max might be able to make 12:1 CR work but he's got access to more state of the equipment and talent than the likes of us. And he runs 102RON and water injection.
High CR might be okay if you need to protect the gearbox, otherwise it depends on the power delivery you want. Personally I'd go lower to give the freedom to choose high boost should I want it, but that's just me.
Do you want a smooth build up or a massive thump in the back?
I've looked into other pistons but these 82mm Arias only come in (an advertised) 9.2:1 at the lowest. I ordered the 9.5:1 because I was going to run the thicker saic N-series gasket (I couldn't in the end as the bore is too small Ford the apart conversion). So the best I could achieve by buying new pistons would be a reduction of 0.3 points. I'd be better off modifying the pistons I have. The biggest problem I had when I started this project was sourcing suitable pistons. The short rod and stubby piston doesn't lend itself to a strong low compression setup.
I'm half-way through modifying my head and I'm pleased with the results. I should get down to 10.8:1 just with the combustion chamber fettling (only finding 3cc of the purported 6cc you can remove - maybe because my head has been skimmed). I'm being fairly conservative and keeping the shape pretty much the same.
If I need more than that I could modify the pistons for an extra 2cc (for 10.5:1) or 3cc (for 10.3:1). I'm still not comfortable doing that. They are meatier than the Wossners but given my previous failure, any weakening of pistons gives me the shakes! Is it worth it for a max of 0.5 points reduction? Especially considering i would have to have to remove the ceramic coating and have it redone after I'd I really want it. I'd also have to find someone to do this for me. Maybe scholar.
I'm half-way through modifying my head and I'm pleased with the results. I should get down to 10.8:1 just with the combustion chamber fettling (only finding 3cc of the purported 6cc you can remove - maybe because my head has been skimmed). I'm being fairly conservative and keeping the shape pretty much the same.
If I need more than that I could modify the pistons for an extra 2cc (for 10.5:1) or 3cc (for 10.3:1). I'm still not comfortable doing that. They are meatier than the Wossners but given my previous failure, any weakening of pistons gives me the shakes! Is it worth it for a max of 0.5 points reduction? Especially considering i would have to have to remove the ceramic coating and have it redone after I'd I really want it. I'd also have to find someone to do this for me. Maybe scholar.
Edited by Stuballs on Monday 15th August 14:14
Ive said:
if you remove 2mm from the center of the crown, 70mm diameter, you'll gain 8cc. You could leave a 1mm dome in the center, if the crown thickness is below 5mm.
That's actually a good point. Even taking 1mm out gets me 4cc. With the head fettling gaining me 3cc I gain a total of 7cc, reducing CR to 10:1. I would just need to find someone I can trust to modify the pistons - then get them ceramic coated again.I'm still trying to get to the bottom of how this happened. I'm getting inconsistent information from various sources so I'll not say anything for now.
Bloody glad I checked the CR and didn't just bolt this lot together.
Ive said:
sounds like these pistons are intended for an other engine, e.g. a Honda B16 with +1mm bore.
these engines have 40+cc chamber volume in combination with a lower swept volume.
Sounds like there are at least two expensive piston manufacturers who haven't done their homework properly..these engines have 40+cc chamber volume in combination with a lower swept volume.
I'm about to start a supercharger conversion on the K series VVC engine in my Triumph Spitfire and have been following this thread with interest. I managed to buy a used Turbo Technics 260 kit which TT used to offer for Elises. Along with the supercharger I bought the pistons and rods which TT fitted. Given the discussion on pistons on this thread I thought it might be interesting to share some pictures of the pistons they used. They are marked TT, so presumably their own design, but Lord knows who made them. They also came with similarly marked, forged rods. I know that the engine has done about 3000 track miles, and I can't find any damage or signs of damage or detonation, so they can't be too bad, however, I have yet to measure or fit the rods, so don't know what the length, CR or squish is like. However, as an example of a set up which has worked for some time under hard use, hopefully you might find the pictures useful.
Best of luck with your project, it looks like you've gone to great lengths to do things properly and I'm sure your perseverance will pay off in the end.![](http://thumbsnap.com/sc/28U9vxrp.jpg[/img]</a> <a href="http://thumbsnap.com/hWRlGR8Z" Target="_blank" rel="nofollow">[img]http://thumbsnap.com/sc/hWRlGR8Z.jpg)
Best of luck with your project, it looks like you've gone to great lengths to do things properly and I'm sure your perseverance will pay off in the end.
itiejim said:
I'm about to start a supercharger conversion on the K series VVC engine in my Triumph Spitfire and have been following this thread with interest. I managed to buy a used Turbo Technics 260 kit which TT used to offer for Elises. Along with the supercharger I bought the pistons and rods which TT fitted. Given the discussion on pistons on this thread I thought it might be interesting to share some pictures of the pistons they used. They are marked TT, so presumably their own design, but Lord knows who made them. They also came with similarly marked, forged rods. I know that the engine has done about 3000 track miles, and I can't find any damage or signs of damage or detonation, so they can't be too bad, however, I have yet to measure or fit the rods, so don't know what the length, CR or squish is like. However, as an example of a set up which has worked for some time under hard use, hopefully you might find the pictures useful.
Best of luck with your project, it looks like you've gone to great lengths to do things properly and I'm sure your perseverance will pay off in the end.
The TT rods are 2mm shorter than stock NA rods, they arnt forged according to last time i spoke to turbotechnics and the pistons ae hypereutectic pistons with an overall compression ratio of 8.5:1.Best of luck with your project, it looks like you've gone to great lengths to do things properly and I'm sure your perseverance will pay off in the end.
The highest ive ever seem them been run is 235bhp in a lotus elise on Emeralds dyno, again vvc engine, they were claimed to have been run at close to 260bhp on the exige vhpd, but they had problems is mains bearing wear as they tried to use ARP head studs rather than normal stretch bolts.
Most people who turbo or supercharge go down the shorter rod route for ease of use
That's useful information, thanks. I will continue to run the VVC cams with an Emerald ECU. Dave Walker tells me that they did manage to get 260 bhp out of those kits, however, apparently they had to run very lumpy cams and struggled to get them to idle nicely and work well on the road. I'll be looking for a more flexible, hopefully reliable build and am happy to sacrifice some horses to get that. Out of interest, I can't claim to recognise the difference, but TT advertised the 260 kit has having forged rods: http://www.turbotechnics.com/cars/TT260.htm:
These pistons look like they've been putting up with the abuse in the VHPD engine they came out of though, so hopefully they can help the OP resolve his problems.
These pistons look like they've been putting up with the abuse in the VHPD engine they came out of though, so hopefully they can help the OP resolve his problems.
the TT rods are forged as are the OEM ones.
Short rods and 8000 rpm rev limits are not the way forward. Thrust loads get enormous.
If you stay at a sensible 7000 rpm rev limit, you'll be fine with that TT combo. I'd combine them with nodular cast iron liners from Westwood for the extra strengh. OEM liners tend to crack sometimes once you apply high revs and or forced induction.
Short rods and 8000 rpm rev limits are not the way forward. Thrust loads get enormous.
If you stay at a sensible 7000 rpm rev limit, you'll be fine with that TT combo. I'd combine them with nodular cast iron liners from Westwood for the extra strengh. OEM liners tend to crack sometimes once you apply high revs and or forced induction.
Stu,
just read this on SELOC from a chap running a SC 1.9l Rover K. I hope he is fine with the citation.
"The pistons came from the States and were supposed to give 9.5:1 but actually gave 10.75:1! "
He put in a 1m shim to reduce the CR.
This pretty much confirms that these 82mm pistons' CR are specified for an other type engine. there was no 1.9l K ever from the factory. So that makes sense.
I'd still consider machining the pistons after measures the crown thickness.
just read this on SELOC from a chap running a SC 1.9l Rover K. I hope he is fine with the citation.
"The pistons came from the States and were supposed to give 9.5:1 but actually gave 10.75:1! "
He put in a 1m shim to reduce the CR.
This pretty much confirms that these 82mm pistons' CR are specified for an other type engine. there was no 1.9l K ever from the factory. So that makes sense.
I'd still consider machining the pistons after measures the crown thickness.
Edited by Ive on Thursday 18th August 22:46
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