Racing Beat exhaust dyno compairisons
03-02-09, 04:22 PM
#27
Thanks for doing that DJ. They were both Dynojets 8.8 miles of eachother. Also there are dyno sheets from friends with a veriance of only 2-3 whp, and that can be attributed to temprature and humidity changes.
I just love the TQ curve..
I just love the TQ curve..
03-02-09, 05:14 PM
#28
It's been known for some time that the SDJ header, which is no longer produced but the patent rights are owned by a former member, has always produced the greatest hp gain. The reasoning is simple. The SDJ comes straight off the block 3" before it begins it's curve. That short straight shot reduces back presure nothing more, nothing less. I also happen to have an RE header on the widebody. Just laying it side by side to the RB header, one immediately notices the difference. The addition of the megaphone adds even more hp, though that part I've never understood how or why.
If one wants to learn more about exhaust, read the the exhaust chapter in "HOW TO MODIFY YOU RX7" BY Dave Emanuel and Jim Downing. Link to online book is as follows:
http://foxed.ca/rx7manual/manuals/ho...20your%20rx-7/
If one wants to learn more about exhaust, read the the exhaust chapter in "HOW TO MODIFY YOU RX7" BY Dave Emanuel and Jim Downing. Link to online book is as follows:
http://foxed.ca/rx7manual/manuals/ho...20your%20rx-7/
03-02-09, 07:45 PM
#30
So since Saturday I've been really excited that it did 189. All happy walking around with a smile, but now it's settling in and I'm a little disappointed. Only 10.35 more whp until I crack 200. I need 200, I need it, damn it, I need it nooooowwww! lol rotaries are like crack I tell you.
03-02-09, 09:31 PM
#33
I already run 43mm venturies. I'll just throw them away and see how that works. lol. plugs are always new the day of the dyno. and I run RP 20w-50. I guess I could just run 5w for the number then drain it. I'll never run oil that light on a rotary.
03-02-09, 10:57 PM
#34
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The first number means nothing once the oil is fully warmed up. 0W-30 is the same as 5W-30, which is the same as 10W-30 at operating temp. They're all 30 weight oils. 0W-30 just doesn't put as much wear on your engine at cold startup. But even then, at cold startup the oil is way thicker than what you want. That's why we warm up our cars before driving them hard.
03-02-09, 11:08 PM
#35
The first number means nothing once the oil is fully warmed up. 0W-30 is the same as 5W-30, which is the same as 10W-30 at operating temp. They're all 30 weight oils. 0W-30 just doesn't put as much wear on your engine at cold startup. But even then, at cold startup the oil is way thicker than what you want. That's why we warm up our cars before driving them hard.
thats not true. I never warm up my rotaries coz it will wake up the entire neighborhood. I start and go.
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Rx7fb spirit r (01-27-20)
03-02-09, 11:40 PM
#36
As for why megaphone work, its because of high and low pressures inside the exhaust. A high pressure(smaller area pipe) zone is the one coming out of the headers, and the low pressure zone (bigger area pipe).The sooner you can introduce that low pressure (after the collector), the higher the pressure left in the smaller pipe (the headers), so its a bigger difference in pressure at that point therefore creating a bigger draw/pull of exhaust gases.
It's kinda like the weather where a high pressure front will always move to a low pressure front . Another example is a pressure cooker, pull the piece that holds all the steam in and watch all the steam get pulled out from the high pressure inside the cooked to the surounding air at a high speed.
Where reverse cone comes in though I'm not sure. But then again I believe it was Rotary God that once said that reverse cone doesn't have much effect on a rotary but more on a piston engine. It could be to try to keep an area hotter to pull more gases from the cylinders because they don't have a constant flow like we do.
A quick google search of expansion chamber:
http://www.froggy.se/skalmanmc/rd350/tuning/expan1.htm
Pretty interesting info, but as you can tell more for piston engines. And those are some pretty wild but not unpopular style of expansion chambers for a 2 stroke.
03-03-09, 05:48 PM
#37
If you go back to the thread someone questioned him and he said he bought the car from a friend who bought the RB exhaust. It is RB, and if I hadn't given my old one away i would've cut it open to show, but I thought it was already covered that their muffler wasn't free flowing, but chambered. You can look inside the muffler with a flash light and see it's exactly as it's pictured above. Typical chambered muffler.
03-04-09, 12:07 AM
#41
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So since Saturday I've been really excited that it did 189. All happy walking around with a smile, but now it's settling in and I'm a little disappointed. Only 10.35 more whp until I crack 200. I need 200, I need it, damn it, I need it nooooowwww! lol rotaries are like crack I tell you.
10 more hp should be doable, you gotta go and look at everything. is the air filter big enough? cap and rotor? race plugs might help you at this point too. lighter oils would help too, the competition prep book recommends 30 weight oil.
dunno if you wanna get this nuts but the spec miata people do a lot of work on reducing drivetrain losses, you know you're nuts when you're swapping transmissions and then dragging the car around with a fish scale....
03-04-09, 01:25 AM
#42
that tq curve looks like FUN
10 more hp should be doable, you gotta go and look at everything. is the air filter big enough? cap and rotor? race plugs might help you at this point too. lighter oils would help too, the competition prep book recommends 30 weight oil.
dunno if you wanna get this nuts but the spec miata people do a lot of work on reducing drivetrain losses, you know you're nuts when you're swapping transmissions and then dragging the car around with a fish scale....
10 more hp should be doable, you gotta go and look at everything. is the air filter big enough? cap and rotor? race plugs might help you at this point too. lighter oils would help too, the competition prep book recommends 30 weight oil.
dunno if you wanna get this nuts but the spec miata people do a lot of work on reducing drivetrain losses, you know you're nuts when you're swapping transmissions and then dragging the car around with a fish scale....
I ran new rx8 plugs on leading with Mallory powering FC coil for direct fire, so that's not the issue. i dyno'd w/o air filter. I rarely run one. i'm working on getting my Weds Superfins fixed so those can replace the super heavy Enkie 92's on the car now. i run full synth royal purple 25-50 changed it about 500 miles ago, so I don't think going lighter would net more than 2-3 whp. I'm going to play with the carb some more, get an under drive pully, and pull the manifold off and port it.
And FYI Rx-8 plugs are amazing. They start easier and have less misses than any other plug I've ever run and they fit perfect in any 13B housing. I've heard of people cutting the washer off of spark plugs to get a little higher compression with the plug closer to the housing face. I'm going to try it on a spare housing and see if it causes any clearance issues.
03-04-09, 01:54 PM
#45
just a good comparison of spark plugs website:
http://www.silverbulletrx7.com/plugs/
Although the Rx-8's plugs are not included he did mention he will be doing that sometime. Also there are some interesting plugs in there.
http://www.silverbulletrx7.com/plugs/
Although the Rx-8's plugs are not included he did mention he will be doing that sometime. Also there are some interesting plugs in there.
03-04-09, 03:56 PM
#46
just a good comparison of spark plugs website:
http://www.silverbulletrx7.com/plugs/
Although the Rx-8's plugs are not included he did mention he will be doing that sometime. Also there are some interesting plugs in there.
http://www.silverbulletrx7.com/plugs/
Although the Rx-8's plugs are not included he did mention he will be doing that sometime. Also there are some interesting plugs in there.
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THRILCKR (07-25-19)
03-04-09, 04:44 PM
#47
I have B7EIX in my REPU and they're the best plug I've ever used on the street. Starts easier, much improved throttle response, and the tailpipe doesn't smell as bad.
13b n/a streetport, 4 port.
Back on subject, if you increase the timing to 30* you'll get about 4 more hp but that's not a safe amount of advance - right on the ragge dedge. And upgrading to a 51mm IDA would help your top end and get more hp, but keep in mind the torque curve will move up 1000rpms as there's less velocity, so less low end. You can mess around with annual auxiliary venturi's but that upgrade is extremely pricey so you start to ask why not just go EFI and get better drivability and MPG too? Nice work by the way.
13b n/a streetport, 4 port.
Back on subject, if you increase the timing to 30* you'll get about 4 more hp but that's not a safe amount of advance - right on the ragge dedge. And upgrading to a 51mm IDA would help your top end and get more hp, but keep in mind the torque curve will move up 1000rpms as there's less velocity, so less low end. You can mess around with annual auxiliary venturi's but that upgrade is extremely pricey so you start to ask why not just go EFI and get better drivability and MPG too? Nice work by the way.
03-04-09, 06:27 PM
#48
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It is fun... lqtm
I ran new rx8 plugs on leading with Mallory powering FC coil for direct fire, so that's not the issue. i dyno'd w/o air filter. I rarely run one. i'm working on getting my Weds Superfins fixed so those can replace the super heavy Enkie 92's on the car now. i run full synth royal purple 25-50 changed it about 500 miles ago, so I don't think going lighter would net more than 2-3 whp. I'm going to play with the carb some more, get an under drive pully, and pull the manifold off and port it.
And FYI Rx-8 plugs are amazing. They start easier and have less misses than any other plug I've ever run and they fit perfect in any 13B housing. I've heard of people cutting the washer off of spark plugs to get a little higher compression with the plug closer to the housing face. I'm going to try it on a spare housing and see if it causes any clearance issues.
I ran new rx8 plugs on leading with Mallory powering FC coil for direct fire, so that's not the issue. i dyno'd w/o air filter. I rarely run one. i'm working on getting my Weds Superfins fixed so those can replace the super heavy Enkie 92's on the car now. i run full synth royal purple 25-50 changed it about 500 miles ago, so I don't think going lighter would net more than 2-3 whp. I'm going to play with the carb some more, get an under drive pully, and pull the manifold off and port it.
And FYI Rx-8 plugs are amazing. They start easier and have less misses than any other plug I've ever run and they fit perfect in any 13B housing. I've heard of people cutting the washer off of spark plugs to get a little higher compression with the plug closer to the housing face. I'm going to try it on a spare housing and see if it causes any clearance issues.
i know of a t2 back in the day they did an underdrive pulley on and it picked up something unbelievable like 22hp or something. car was pretty stock too
03-04-09, 07:19 PM
#49
weird. I had an underdrive on my last car and it only gave me 2whp...
The trailing plug on the rx8's is actually shorter. it's reach is 19mm while the leading is 20.6. all stock NGK FB and FC plugs reach 20.6. The plugs you gotta watch out for are denso's. Their irridums are 21 and the regular FC plugs are 21.5 L and 20.6 T
The trailing plug on the rx8's is actually shorter. it's reach is 19mm while the leading is 20.6. all stock NGK FB and FC plugs reach 20.6. The plugs you gotta watch out for are denso's. Their irridums are 21 and the regular FC plugs are 21.5 L and 20.6 T