NA C6z Build
08-26-2022, 11:35 AM
#161
What's the compression limit with pump E85. I don't want to have to spike the tank every time I want to beat on the car. The compression ratio with the new pistons is going to be a little spicy. It's going to be 15.3-15.8 depending on what gasket thickness we decide to run. Cam specs at .006" are 318/334 115+6. Dynamic compression is coming out to 9.8 and effective ratio is 9.3.
Torn on exhaust. I want to keep it as light weight as possible. I don't have enough room to put mufflers directly under the car, without running them all the way out back. I was thinking of deleting the factory fuel tanks and running a single fuel cell in the back of the car. Then I can route the exhaust out the sides. That should help with some of the drone (I hope). On top of aiding traction with the weight distribution.
My heads/lower intake are getting worked over by Iron Mask Airflow. He's been doing some great work lately. I have no doubts he can work some magic on my stuff.
Plan is to go with a Mantic twin disc cerametallic clutch. This should drop ~15lbs over the Monster twin that's in the car and have significantly less MOI due to the overall smaller design. I've had one of these clutches in my last car and I loved how it drove and shifted.
The TB is the only thing I don't see making a huge difference. But might as well try and see what it will do.
Unfortunately, the bottom end rebuild wasn't planned and I don't want the car to sit for an extended period of time. This is the reason I will not be switching to a solid roller at this time. I believe there is more to gain with the current one still. Regardless, I don't think I will be disappointed.
Not sure if I will do the final tuning on this one. I purchased a Holley course to try an learn a little more. Still have some time to decide. I'm confident in my ability to dial in the fuel table (the easy part) but its the timing table that is over my head.
Torn on exhaust. I want to keep it as light weight as possible. I don't have enough room to put mufflers directly under the car, without running them all the way out back. I was thinking of deleting the factory fuel tanks and running a single fuel cell in the back of the car. Then I can route the exhaust out the sides. That should help with some of the drone (I hope). On top of aiding traction with the weight distribution.
My heads/lower intake are getting worked over by Iron Mask Airflow. He's been doing some great work lately. I have no doubts he can work some magic on my stuff.
Plan is to go with a Mantic twin disc cerametallic clutch. This should drop ~15lbs over the Monster twin that's in the car and have significantly less MOI due to the overall smaller design. I've had one of these clutches in my last car and I loved how it drove and shifted.
The TB is the only thing I don't see making a huge difference. But might as well try and see what it will do.
Unfortunately, the bottom end rebuild wasn't planned and I don't want the car to sit for an extended period of time. This is the reason I will not be switching to a solid roller at this time. I believe there is more to gain with the current one still. Regardless, I don't think I will be disappointed.
Not sure if I will do the final tuning on this one. I purchased a Holley course to try an learn a little more. Still have some time to decide. I'm confident in my ability to dial in the fuel table (the easy part) but its the timing table that is over my head.
You can fit a dual 3" inlet/outlet 5x8 oval muffler in the tunnel just have to hang it perfectly, that allows it to be dumped under the car and bearable noise wise. The other option is two offset 3" race mufflers they are only 4" external diameter and a foot long, those dumped out the sides would be nice and a bit lighter. I've used the TotalFlow brand on Amazon on a bunch of builds and they work pretty well.
I liked the Mantic as well, it drove great but it did not like launches on sticky tires!
Just sneak up on it and keep an eye on your plugs and getting the timing dialed in isn't too bad. I'd rescale the map for a big cam NA car so you have more resolution.
That’s a whole lot lighter than I’d expect … my Miata is very light for an LS swap because it’s pretty stripped (no AC, PS, power windows, stereo, etc.), and it’s still at 2400 lbs. Most Miata swaps run closer to 2600. The ‘vette is so much bigger, it’s surprising to me you can get it down to that weight.
The following 2 users liked this post by SLOW SEDAN:
DualQuadDave (08-26-2022), logan2ss (08-31-2022)
08-26-2022, 12:14 PM
#162
I'll be swapping my RPS to a Tilton 246 in my street car if you're interested in an even lighter clutch that would cost a lot less than a new Mantic I plan to sell it soon. Honestly though you'd be best off for your goals getting a tilton 5.5" or similar. The weight off the engine, plus out of the car entirely would be huge. The tiltons with flexplate are like 10 pounds total at a 5.5" diameter. There are a few on this site that have put lots of street miles on theirs.
With pump e85 I don't think you can expect enough octane to run over 15:1. I think you have to assume worst case you wind up with 100 octane R+M/2 to be safe. Rocket rates their 100 octane to 14:1 and below, and their E85 112 octane up to 16:1. You're in the territory where getting it wrong means another shortblock at a minimum.
With pump e85 I don't think you can expect enough octane to run over 15:1. I think you have to assume worst case you wind up with 100 octane R+M/2 to be safe. Rocket rates their 100 octane to 14:1 and below, and their E85 112 octane up to 16:1. You're in the territory where getting it wrong means another shortblock at a minimum.
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jayyyw (08-27-2022)
08-26-2022, 04:22 PM
#163
ModSquad
iTrader: (6)
I'll be swapping my RPS to a Tilton 246 in my street car if you're interested in an even lighter clutch that would cost a lot less than a new Mantic I plan to sell it soon. Honestly though you'd be best off for your goals getting a tilton 5.5" or similar. The weight off the engine, plus out of the car entirely would be huge. The tiltons with flexplate are like 10 pounds total at a 5.5" diameter. There are a few on this site that have put lots of street miles on theirs.
With pump e85 I don't think you can expect enough octane to run over 15:1. I think you have to assume worst case you wind up with 100 octane R+M/2 to be safe. Rocket rates their 100 octane to 14:1 and below, and their E85 112 octane up to 16:1. You're in the territory where getting it wrong means another shortblock at a minimum.
With pump e85 I don't think you can expect enough octane to run over 15:1. I think you have to assume worst case you wind up with 100 octane R+M/2 to be safe. Rocket rates their 100 octane to 14:1 and below, and their E85 112 octane up to 16:1. You're in the territory where getting it wrong means another shortblock at a minimum.
The following 2 users liked this post by Che70velle:
Corona (08-26-2022), DualQuadDave (08-26-2022)
08-27-2022, 10:39 AM
#164
TECH Fanatic
Thread Starter
I'll be swapping my RPS to a Tilton 246 in my street car if you're interested in an even lighter clutch that would cost a lot less than a new Mantic I plan to sell it soon. Honestly though you'd be best off for your goals getting a tilton 5.5" or similar. The weight off the engine, plus out of the car entirely would be huge. The tiltons with flexplate are like 10 pounds total at a 5.5" diameter. There are a few on this site that have put lots of street miles on theirs.
With pump e85 I don't think you can expect enough octane to run over 15:1. I think you have to assume worst case you wind up with 100 octane R+M/2 to be safe. Rocket rates their 100 octane to 14:1 and below, and their E85 112 octane up to 16:1. You're in the territory where getting it wrong means another shortblock at a minimum.
With pump e85 I don't think you can expect enough octane to run over 15:1. I think you have to assume worst case you wind up with 100 octane R+M/2 to be safe. Rocket rates their 100 octane to 14:1 and below, and their E85 112 octane up to 16:1. You're in the territory where getting it wrong means another shortblock at a minimum.
08-27-2022, 12:14 PM
#165
TECH Fanatic
Thread Starter
Nice! Ya NA you should be able to get it damn light! A certain C6Z build going on right now may very well beat my 2200lb NA weight.
What fuel pump do you have? Thought about running E with 50% meth? The plastic fuel tanks were about 40lbs so going to a fuel cell saved a good bit. Guess if you ditch the stock tanks you need a new pump anyways!
You can fit a dual 3" inlet/outlet 5x8 oval muffler in the tunnel just have to hang it perfectly, that allows it to be dumped under the car and bearable noise wise. The other option is two offset 3" race mufflers they are only 4" external diameter and a foot long, those dumped out the sides would be nice and a bit lighter. I've used the TotalFlow brand on Amazon on a bunch of builds and they work pretty well.
I liked the Mantic as well, it drove great but it did not like launches on sticky tires!
Just sneak up on it and keep an eye on your plugs and getting the timing dialed in isn't too bad. I'd rescale the map for a big cam NA car so you have more resolution.
They drop weight fast! NA I got down to 2200lbs with cage and a 5gal fuel cell, twin turbo I'm sitting about 2400 with a mild steel cage and full 15gal fuel cell. If I actually spent money on a carbon hatch, nicer wheels and other things it could drop a lot more weight pretty fast.
What fuel pump do you have? Thought about running E with 50% meth? The plastic fuel tanks were about 40lbs so going to a fuel cell saved a good bit. Guess if you ditch the stock tanks you need a new pump anyways!
You can fit a dual 3" inlet/outlet 5x8 oval muffler in the tunnel just have to hang it perfectly, that allows it to be dumped under the car and bearable noise wise. The other option is two offset 3" race mufflers they are only 4" external diameter and a foot long, those dumped out the sides would be nice and a bit lighter. I've used the TotalFlow brand on Amazon on a bunch of builds and they work pretty well.
I liked the Mantic as well, it drove great but it did not like launches on sticky tires!
Just sneak up on it and keep an eye on your plugs and getting the timing dialed in isn't too bad. I'd rescale the map for a big cam NA car so you have more resolution.
They drop weight fast! NA I got down to 2200lbs with cage and a 5gal fuel cell, twin turbo I'm sitting about 2400 with a mild steel cage and full 15gal fuel cell. If I actually spent money on a carbon hatch, nicer wheels and other things it could drop a lot more weight pretty fast.
My x-pipe is 3.5”. It makes the body of the muffler big enough that there’s really no room to fit it.
08-27-2022, 12:22 PM
#166
TECH Fanatic
Thread Starter
The issue is, my heads are already milled very aggressively. On top of that, pistons are scarce and I was only able to find a set of K0004X130 pistons. These show compression with a 70cc head at 11.5. Maybe I’m calculating it wrong somewhere. Would these increase only an extra .5pt overall or does it increase as the CC volume drops? Maybe I can get the head porter to open the combustion chambers a little to help lower the compression
08-27-2022, 12:26 PM
#167
TECH Senior Member
08-27-2022, 01:23 PM
#168
The issue is, my heads are already milled very aggressively. On top of that, pistons are scarce and I was only able to find a set of K0004X130 pistons. These show compression with a 70cc head at 11.5. Maybe I’m calculating it wrong somewhere. Would these increase only an extra .5pt overall or does it increase as the CC volume drops? Maybe I can get the head porter to open the combustion chambers a little to help lower the compression
Softening the chambers is not a bad idea.
I'll let you know when the clutch is out I'm hoping to get the engine screwed together this Sunday, and then it is time to start wrenching on the car.
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jayyyw (08-27-2022)
08-27-2022, 02:38 PM
#169
TECH Fanatic
Thread Starter
08-27-2022, 02:39 PM
#170
TECH Fanatic
Thread Starter
They're actually ~12.5:1 with .040 quench and zero deck with 70cc heads. I think you have the sign wrong on the dome vs dish. 53cc will be ~15.8:1 at .040 quench.
Softening the chambers is not a bad idea.
I'll let you know when the clutch is out I'm hoping to get the engine screwed together this Sunday, and then it is time to start wrenching on the car.
Softening the chambers is not a bad idea.
I'll let you know when the clutch is out I'm hoping to get the engine screwed together this Sunday, and then it is time to start wrenching on the car.
08-27-2022, 03:16 PM
#171
TECH Enthusiast
08-27-2022, 03:19 PM
#172
TECH Fanatic
Thread Starter
The effective compression ratio is what the engine sees while running. While the static CR is defined simply by the geometry of the engine, the effictive CR is influenced by multiple factors such as the engine geometry, cam timing, intake pressure, connecting rod length, and volumetric efficiency.
It is the effective CR that determines how much the fluid is actually compressed during engine operating and therefore the minimum octane rating necessary to avoid pre-detonation. This is why some engines require 100+ octane with an 11:1 compression ratio while others are perfectly fine on 91 octane with a 13:1 compression ratio. E-85 has an equivalent octane rating of 105, and with an expected operating temperature of around 180°F, the maximum dynamic CR is slightly above 10.5
To get higher VE% from high performance engines, the camshaft intake valve is usually closed significantly after BDC compared to a 'street' type of engine. This later closing intake point helps contribute to additional cylinder filling using 'ramming' properties of the intake flow.
This later closing point reduces the engine's 'effective compression ratio' to below the static compression ratio.
Basically the piston is traveling up from BDC on the compression stroke when the intake valve is still open. This is effectively bleeding off the compression pressure, while still filling the chamber with fresher air/fuel mixture. (better VE%)
It is basically using a percentage of the compression stroke before it starts compressing the fuel/air mixture!
This 'effective compression ratio' can be lower than the popular 'Dynamic Compression Ratio' however. (or even higher depending on cam data)
It calculates all the effects of the cylinder intake pumping and ramming processes with the trapped air/fuel at the intake closing point.
08-27-2022, 08:48 PM
#173
ModSquad
iTrader: (6)
I wouldn’t consider effective ratio. Dynamic ratio is what the engine actually sees (cylinder pressure) according to valve events. Effective ratio…to be 100% accurate to find, requires pressure probes in cylinder. Very very hard to determine.
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02EBC5Z06 (08-31-2022)
08-28-2022, 07:57 AM
#174
TECH Enthusiast
What they do to simplify it is where the camshaft closes at .006 or zero lash lift for solids (basically when intake valve is closed) they calculate how far the piston is up the bore at that valve timing event (Wallace racing calculators has a thing on this). Say on a motor a cam closes intake valve at 72 degrees ADC and based on the stroke and rod length (use a 4 inch stroke here) that is say 75% still left or the piston has come up 25% (1 inch from the bottom of a 4 inch stroke). Then say your compression is 12 to 1 then they take that multiply by 75% and that means a 9 to 1 dynamic compression ratio. Some people make the mistake of using the .050 valve events and come up with some very high number. The 72 degree number above then becomes like 45 degrees. Some calculators can do the .050 they just add like 26-30 degrees to that number in their formula which you never see.
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02EBC5Z06 (08-31-2022)
08-29-2022, 09:26 AM
#175
Ah, 3.5" makes it harder in the tunnel for sure! Considering you can fit turbos and 4" exhaust where the fuel tanks were a simple muffler should be pretty easy to slap in there. Could do aluminum after the xpipe to save some weight, variety of aluminum race mufflers available.
08-31-2022, 08:35 PM
#176
TECH Fanatic
Thread Starter
What they do to simplify it is where the camshaft closes at .006 or zero lash lift for solids (basically when intake valve is closed) they calculate how far the piston is up the bore at that valve timing event (Wallace racing calculators has a thing on this). Say on a motor a cam closes intake valve at 72 degrees ADC and based on the stroke and rod length (use a 4 inch stroke here) that is say 75% still left or the piston has come up 25% (1 inch from the bottom of a 4 inch stroke). Then say your compression is 12 to 1 then they take that multiply by 75% and that means a 9 to 1 dynamic compression ratio. Some people make the mistake of using the .050 valve events and come up with some very high number. The 72 degree number above then becomes like 45 degrees. Some calculators can do the .050 they just add like 26-30 degrees to that number in their formula which you never see.
08-31-2022, 08:39 PM
#177
TECH Fanatic
Thread Starter
I was saying more like 50% of methanol through the fuel system, hard to do that much just spraying in the intake and hoping the distribution is correct unless you have a direct port setup and even then many of those pumps can't supply enough volume.
Ah, 3.5" makes it harder in the tunnel for sure! Considering you can fit turbos and 4" exhaust where the fuel tanks were a simple muffler should be pretty easy to slap in there. Could do aluminum after the xpipe to save some weight, variety of aluminum race mufflers available.
Ah, 3.5" makes it harder in the tunnel for sure! Considering you can fit turbos and 4" exhaust where the fuel tanks were a simple muffler should be pretty easy to slap in there. Could do aluminum after the xpipe to save some weight, variety of aluminum race mufflers available.
I'm going to do it out of titanium. there are a few places that sell nice titanium mufflers.
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DualQuadDave (09-01-2022)
09-01-2022, 11:07 AM
#180
Titanium isnt overly expensive if you supply the materials yourself. Dont do aluminum exhaust, it will crack guaranteed. Ticon industries makes great Ti mufflers and vibrant sells 1 meter tubes (3.2ft) sections in 3.5 for $175. The best way to do it is to buy all the materials and mock it up then bring to a competent welder that has Ti experience and is going to thoroughly prep the material and back purge the **** out of it. Im building my own dual 3.5” setup on my Rx7 soon.