Rover 200 BRM - 1.8 K-Series turbo project
Discussion
I thought I had better check my static compression ratio. The piston supplier told me they lower the compression ratio to about 9:1, but I wanted to measure it for myself. There are other variables involved so having a base reading will help me decide what direction to go on other aspects of the build (headwork, gasket choice).
The process:
I got a cheap burette (A-Level Chemistry comes screaming back to me) and a 10mm thick acrylic plate off ebay. The idea is that you sit the acrylic plate on the liner (sealed with some grease), then dribble a measured amount of fluid through a hole in it until it reaches the top of the plate. For the fluid I used rubbing alcohol with blue food dye in it. Obviously the cylinder you're measuring has to be at TDC.
Starting with the piston top:
And moving onto the cylinder head:
Results:
Volume above piston (to flush with liner): 16.4cc
Combustion chamber: 30.2cc
I know the piston swept volume is 448.9cc
If we assume a 1mm thick compressed head gasket, the volume of that is 5cc
Note: with this method I have probably not measured the volume above the first compression ring, but below the piston deck. This amount is probably well under 1cc so I'm not too concerned.
Volume at BDC / Volume at TDC = 500.5/51.6 = 9.7
These figures give a compression ratio of 9.7:1
This exercise has highlighted how dramatic material removal from the combustion chamber from headwork can be. You can reportedly remove up to 6cc from the VVC head's combustion chamber. Removing this much would reduce CR to 8.8.
What I found interesting was how little relative effect a skim would have. The maximum recommended 0.2mm skim would reduce the combustion chamber by less than 1cc (on my figures increasing CR from 9.7 to 9.9:1).
The process:
I got a cheap burette (A-Level Chemistry comes screaming back to me) and a 10mm thick acrylic plate off ebay. The idea is that you sit the acrylic plate on the liner (sealed with some grease), then dribble a measured amount of fluid through a hole in it until it reaches the top of the plate. For the fluid I used rubbing alcohol with blue food dye in it. Obviously the cylinder you're measuring has to be at TDC.
Starting with the piston top:
And moving onto the cylinder head:
Results:
Volume above piston (to flush with liner): 16.4cc
Combustion chamber: 30.2cc
I know the piston swept volume is 448.9cc
If we assume a 1mm thick compressed head gasket, the volume of that is 5cc
Note: with this method I have probably not measured the volume above the first compression ring, but below the piston deck. This amount is probably well under 1cc so I'm not too concerned.
Volume at BDC / Volume at TDC = 500.5/51.6 = 9.7
These figures give a compression ratio of 9.7:1
This exercise has highlighted how dramatic material removal from the combustion chamber from headwork can be. You can reportedly remove up to 6cc from the VVC head's combustion chamber. Removing this much would reduce CR to 8.8.
What I found interesting was how little relative effect a skim would have. The maximum recommended 0.2mm skim would reduce the combustion chamber by less than 1cc (on my figures increasing CR from 9.7 to 9.9:1).
Edited by Stuballs on Wednesday 4th October 14:05
Stuballs said:
Seats could be more supportive but this will be a road car so I'm not too worried. The interior is one of the BRM's style points (love it or hate it) so it would be a shame to lose that for some aftermarket bucket seats.
Ooh, retrim some buckets in the same materials...Edited by Polynesian on Sunday 15th November 20:29
turbotoaster said:
eeek 9.7:1 thats not great news if I want to throw 28psi of boost through it to make the 400bhp, looks like im going to have to make sure I take some material out of the head and maybe run a ferriday head saver to give it a little more of a drop, thanks for checking this
Hi LeeIf you take 5 or 6cc out of the top of the combustion chamber even with a 1mm elastomer gasket you'll get to around 9:1. If you use an MLS or the n-series gasket you'll get closer to 8.5 or 8:1.
An alternative would be to source the maxspeeding turbo spec rods (2mm shorter?). That'll take you below 8:1 for really high boost.
I remember cc'ing the head and combustion chamber during my apprenticeship. I hated it. The tap on the pipette was so fiddly and fragile - I was terrified I would knock it off it's perch and flood the floor with red fluid!
Another secret admirer of the BRM here - looking forward to seeing this progress.
Another secret admirer of the BRM here - looking forward to seeing this progress.
Alias218 said:
I remember cc'ing the head and combustion chamber during my apprenticeship. I hated it. The tap on the pipette was so fiddly and fragile - I was terrified I would knock it off it's perch and flood the floor with red fluid!
Another secret admirer of the BRM here - looking forward to seeing this progress.
That's exactly what happened the second time I tried to measure the head volume when I got the ported head back - after measuring the first two cylinders I just nudged the burette at the top and the whole thing exploded! that was one of my few "F***-it that'll do. I'm sure it's fine" moments on this build! In fairness, the guy that ported my head hadn't actually touched the combustion chambers and I got the same readings as with the dummy head on cyls 1 and 2 (the eagle eyed K-series aficionados will note that the head in the above pictures is the lesser mpi head that comes with the non-VVC engines and has smaller less-well-designed ports and smaller valves than the VVC - I'll be using a ported VVC head with solid piper cams - more on that later).Another secret admirer of the BRM here - looking forward to seeing this progress.
I must say I'm actually surprised at how many people are enjoying the BRM. Really guys thanks for all the comments! I'll keep the updates coming!
Cue the haters...
I had one of these brand new, I had a track day booked at Combe in my TVR but it had to go to the factory for a speed six engine problem (surprise) so I took the BRM, it shocked quite a few people and I still have a pick of me overtaking a Ferrari 348 in it on the garage wall.
I didn't lose any money on that car when I sold it as it was heavily discounted by HASLEMERE Rover and then they had a woman walk in asking for them to track one down for her so they sold it for me.
That little engine used to love to rev and the grip with the diff was great.
I didn't lose any money on that car when I sold it as it was heavily discounted by HASLEMERE Rover and then they had a woman walk in asking for them to track one down for her so they sold it for me.
That little engine used to love to rev and the grip with the diff was great.
Max_Torque said:
Kinda depends on how much combustion optimisation work you do. I run a CR of over 11:1 with 360kPa(abs) plenum pressure..........
Holy moly that's a lot of boost, even not at that CR. How on earth is that not det'ing all over the shop? Must be some sort of ethanol top fuel dragster or something!Edit: Just did a quick Google and top fuel dragsters run at typically 6.5:1. You, Sir, are some sort of wizard.
Edited by Alias218 on Monday 16th November 19:47
Alias218 said:
Max_Torque said:
Kinda depends on how much combustion optimisation work you do. I run a CR of over 11:1 with 360kPa(abs) plenum pressure..........
Holy moly that's a lot of boost, even not at that CR. How on earth is that not det'ing all over the shop? Must be some sort of ethanol top fuel dragster or something!Edit: Just did a quick Google and top fuel dragsters run at typically 6.5:1. You, Sir, are some sort of wizard.
Edited by Alias218 on Monday 16th November 19:47
A little bit about the turbo I'll be using. I wanted something with a fast spool for minimal lag, giving good power throughout the rev range at moderate boost - 14-16psi at most.
The standard unit on the k-turbo is a gt2052. Not terribly efficient and runs out of puff at 220bhp-ish by which point it's blowing a lot of hot air.
I opted for a T28 from a Nissan 200SX S15 which I know fits the stock manifold. The s15 has a ball bearing turbo and I had it rebuilt with a nice new billet compressor wheel (arguably no real improvement from a normal wheel but the blades had some nicks so was worth doing). This turbo is very similar to the GT2560R which should be perfect for my requirements. If I can get everything else right, this turbo should be good for 250bhp - 300bhp.
GT2560R
Compressor map for the GT2560R for those interested:
Some pics of the turbo after getting it back from refurbing:
I mocked it up to see what it would look like. At this point I realised I was going to have to mount the fans on the front of the rad or possibly move the rad forward.
As you can see, I'm sticking with the standard log manifold. It's actually not that bad. It will be port matched with the head and given a good fettle inside to improve flow.
And ceramic coated by zircotec to help keep engine bay temps down:
The standard unit on the k-turbo is a gt2052. Not terribly efficient and runs out of puff at 220bhp-ish by which point it's blowing a lot of hot air.
I opted for a T28 from a Nissan 200SX S15 which I know fits the stock manifold. The s15 has a ball bearing turbo and I had it rebuilt with a nice new billet compressor wheel (arguably no real improvement from a normal wheel but the blades had some nicks so was worth doing). This turbo is very similar to the GT2560R which should be perfect for my requirements. If I can get everything else right, this turbo should be good for 250bhp - 300bhp.
GT2560R
Compressor map for the GT2560R for those interested:
Some pics of the turbo after getting it back from refurbing:
I mocked it up to see what it would look like. At this point I realised I was going to have to mount the fans on the front of the rad or possibly move the rad forward.
As you can see, I'm sticking with the standard log manifold. It's actually not that bad. It will be port matched with the head and given a good fettle inside to improve flow.
And ceramic coated by zircotec to help keep engine bay temps down:
Edited by Stuballs on Wednesday 4th October 14:08
Max_Torque said:
Despite what the "internet" will tell you, a genuine 270bhp in a short geared, fwd, light car like the 200 will make for a fast car........
Totally agree!!!My turbo'd r53 mini on low boost makes just over 300bhp and will dispatch most things and I'd imagine the 200 will be lighter
Edited by Loui on Monday 16th November 22:46
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