ghetto 4 rotor build
04-13-07, 03:27 PM
#78
The General RE
Originally Posted by speedturn
Don't use the RB "Y" pipes; they do not have a big enough throat for a collector. Send them back and get your money back.
Or use a pipe expander to make it the right size. Throat is one of the most important variables.
04-13-07, 06:47 PM
#79
I think I chose correctly because:
A. ports are 12A size
B. when one is flowing, the other isn't due to 180° rotor phasing
C. constant diameter keeps velocity high
D. limited available space in engine bay and under car
E. center section is already purchased and installed
F. accoustic canceling effect allows street use without choking it down with a bunch of mufflers
A. ports are 12A size
B. when one is flowing, the other isn't due to 180° rotor phasing
C. constant diameter keeps velocity high
D. limited available space in engine bay and under car
E. center section is already purchased and installed
F. accoustic canceling effect allows street use without choking it down with a bunch of mufflers
04-13-07, 07:18 PM
#80
The General RE
This is the reason that I don't like Racing Beat. They post respected specs in their catalog and sell nothing that meets those specs. If you read their Exhaust Tips it recommends a 3 to 4 in² throat area for collectors and 4-5 in² if peripheral ported. This equates to 2 to 2.25" ID or 2.25 to 2.5" ID for peripheral ports. You would need to stretch the ID of their collectors to meet thier own specs.
04-14-07, 02:35 PM
#83
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so whats the part`s list so far and how much have you spent on little odd`s and ends so basically put up all the parts that you have used thus so far to make this project get as far as you have taken it thanks in advance
Last edited by superyakosa22c; 04-14-07 at 02:39 PM. Reason: more ?
04-15-07, 12:35 PM
#86
There are no part numbers because it's all custom or used parts. The only new parts are going to be the rotor housings... maybe. It depends on what the owner can afford.
This is one of those times where "if you have to ask, you'll never know"
This is one of those times where "if you have to ask, you'll never know"
04-21-07, 11:01 PM
#91
if i had to guess at hp levels.... id say around 400hp.... the fellow who operates 3rotor.com built an N/A 3 rotor pp FC and not even broken in made around 300hp with fuel injection.... so i bet my money close to 400hp...
BTW what compression are you going with? stock 12A? or higher?
great results and great concept you got goin on there buddy, keep it up every one og us would absolutely love to see the fruits of your labors
BTW what compression are you going with? stock 12A? or higher?
great results and great concept you got goin on there buddy, keep it up every one og us would absolutely love to see the fruits of your labors
04-22-07, 11:35 AM
#92
Jeezus, thanks for posting that link. It's a good primer for anyone seriously considering a 4 rotor.
cptpain, yeah I was thinking at least 400. Stock 12A compression. '83-'85 rotors. I'll update this thread from time to time when anything new happens. The owner is setting up a shop right now so everything is on hold until it's done.
cptpain, yeah I was thinking at least 400. Stock 12A compression. '83-'85 rotors. I'll update this thread from time to time when anything new happens. The owner is setting up a shop right now so everything is on hold until it's done.
05-25-07, 12:54 AM
#98
Interesting choice on the exhaust.
I was thinking more along the lines of a system that collected at exactly half the distance as the racing beat recommended full length system, collecting that straight from 4 2" ID pipes into 3", and 2 big mufflers under there.
You may as well play on having the power as low as possible in the power band.
I was thinking more along the lines of a system that collected at exactly half the distance as the racing beat recommended full length system, collecting that straight from 4 2" ID pipes into 3", and 2 big mufflers under there.
You may as well play on having the power as low as possible in the power band.
05-25-07, 10:18 AM
#99
Do you think dual 2" into a single 3" will work? The muffler is still up in the air at this point so I'm willing to entertain various ideas.
Each 2" pipe will be flowing all the time since each comes from a pair of rotors. One rotor is always flowing while the other is not - that's how a 2 rotor works - that's why you can get away with a 2" OD header collecting into a single 2" OD pipe.
When one is flowing, the other isn't.
Compare this with a 20B for a moment. You need at least a 2.5" system on a 20B because when one rotor is finishing its exhaust phase, another is beginning, and the third is half way through. A 2" three pipe header collected into a single 2.5" pipe works ok. I experimented with a 2" pipe and the low end was fine but the high end wasn't lol.
Fellow 20B 1st gen owner "Rotary20B" was NA with a ported 20B and a 2.5" system and his engine had plenty up high. It even did well with a turbo but you need a larger pipe because the turbo uses up a lot of the exhaust energy (and noise) so it's best to simply dump it after the turbo with as little restriction as possible. In other words, a 3" system or whatever is ok, which is what he's doing next.
Now back to the 4 rotor. Both pipes in the center section will have full flow all the time like any single pipe system on a 2 rotor. Is it a good idea to collect both pipes into a single 3" system? I just don't know right now.
The original plan was to use an H pipe at some point in the system and continue the dual 2" over the axle and out two seperate mufflers. The H pipe was to prevent the possiblity of sounding like two 12As reving together. Half of the point of this project was for it to sound like a true 4 rotor.
I'm also highly concerned with exhaust gas velocity. The original idea with two mufflers would have kept velocity high since pipe diameter would remain constant through the entire system. Not so when collecting into a 3".
Is anyone out there good with exhaust flow theory?
Each 2" pipe will be flowing all the time since each comes from a pair of rotors. One rotor is always flowing while the other is not - that's how a 2 rotor works - that's why you can get away with a 2" OD header collecting into a single 2" OD pipe.
When one is flowing, the other isn't.Compare this with a 20B for a moment. You need at least a 2.5" system on a 20B because when one rotor is finishing its exhaust phase, another is beginning, and the third is half way through. A 2" three pipe header collected into a single 2.5" pipe works ok. I experimented with a 2" pipe and the low end was fine but the high end wasn't lol.
Fellow 20B 1st gen owner "Rotary20B" was NA with a ported 20B and a 2.5" system and his engine had plenty up high. It even did well with a turbo but you need a larger pipe because the turbo uses up a lot of the exhaust energy (and noise) so it's best to simply dump it after the turbo with as little restriction as possible. In other words, a 3" system or whatever is ok, which is what he's doing next.Now back to the 4 rotor. Both pipes in the center section will have full flow all the time like any single pipe system on a 2 rotor. Is it a good idea to collect both pipes into a single 3" system? I just don't know right now.
The original plan was to use an H pipe at some point in the system and continue the dual 2" over the axle and out two seperate mufflers. The H pipe was to prevent the possiblity of sounding like two 12As reving together. Half of the point of this project was for it to sound like a true 4 rotor.
I'm also highly concerned with exhaust gas velocity. The original idea with two mufflers would have kept velocity high since pipe diameter would remain constant through the entire system. Not so when collecting into a 3".
Is anyone out there good with exhaust flow theory?
05-25-07, 12:25 PM
#100
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Something to consider:
Racing beat pipe is 2" OD with a 1/8" wall, or about a 1.75" ID. That equates to a cross-section of about 2.405 sq. in. Since both pipes are always flowing, it stands to reason that a 4.811 sq. in. cross-section should flow well enough for both. That's about 2.47" ID. If that pipe also has a 1/8" wall, you'd want a ~2.75" OD pipe. Since the peripheral ports will want higher-RPM operation, requiring more flow, and also because 3" pipe is relatively easy to find, I think 3" would be fine.
Just my $0.02.
Racing beat pipe is 2" OD with a 1/8" wall, or about a 1.75" ID. That equates to a cross-section of about 2.405 sq. in. Since both pipes are always flowing, it stands to reason that a 4.811 sq. in. cross-section should flow well enough for both. That's about 2.47" ID. If that pipe also has a 1/8" wall, you'd want a ~2.75" OD pipe. Since the peripheral ports will want higher-RPM operation, requiring more flow, and also because 3" pipe is relatively easy to find, I think 3" would be fine.
Just my $0.02.