Full Bridge Port Crazyness!
Thread Starter
Joined: Dec 2002
Posts: 3,791
Likes: 3
From: Kitchener Ontario Canada
Well a little dissapointing, but with some very good reasons.
First off, we dyno'ed the car with 19" rims on it....probably not the greatest thing to find out the WHP.
Second, the carb needs to be jetted...badly. It pulled pretty hard right up to about 6500-7000 rpm then the carb ran rich and fell right on its face.
We ran it for about 3/4 hour at various rpms under load on the dyno then tried a couple power runs just for fun.
Here is what we came up with:
Basically the carb gives out right when the engine starts to make power and it looks like the HP line is starting to go north. It then hits a rich spot, dips down then bounces back for another burst of power, then dies again.
So if we had some jets for the carb and were able to dial it in all the way to 9500rpm, Id say it will make some pretty decent power.
First off, we dyno'ed the car with 19" rims on it....probably not the greatest thing to find out the WHP.
Second, the carb needs to be jetted...badly. It pulled pretty hard right up to about 6500-7000 rpm then the carb ran rich and fell right on its face.
We ran it for about 3/4 hour at various rpms under load on the dyno then tried a couple power runs just for fun.
Here is what we came up with:
Basically the carb gives out right when the engine starts to make power and it looks like the HP line is starting to go north. It then hits a rich spot, dips down then bounces back for another burst of power, then dies again.
So if we had some jets for the carb and were able to dial it in all the way to 9500rpm, Id say it will make some pretty decent power.
Thread Starter
Joined: Dec 2002
Posts: 3,791
Likes: 3
From: Kitchener Ontario Canada
The TQ numbers are caluclated on the RPM signal which was all over the map, they couldn't get a steady signal, too many other electrical interferances.
The numbers I did see on the screen were around 150-160 TQ.
The numbers I did see on the screen were around 150-160 TQ.
Full Member
Joined: Nov 2003
Posts: 192
Likes: 8
From: .
Rx8 rotors typically need more ignition timing than earlier rotors. With a locked distributor I've found 25-27deg was needed for max power. But the dyno will tell you this anyway, just keep advancing the timing 2 deg at a time until there are no more power gains then back it off a bit.
Wow those are huge chokes! They must be almost non-existant. For a start I would try 43 or 44mm chokes and maybe 130 air correctors. You will also need to go smaller in the main jet with smaller chokes. What size are the pump jets? They affect top end mixtures aswell, the larger the pump jets, the richer it will run up top.
Rx8 rotors typically need more ignition timing than earlier rotors. With a locked distributor I've found 25-27deg was needed for max power. But the dyno will tell you this anyway, just keep advancing the timing 2 deg at a time until there are no more power gains then back it off a bit.
Rx8 rotors typically need more ignition timing than earlier rotors. With a locked distributor I've found 25-27deg was needed for max power. But the dyno will tell you this anyway, just keep advancing the timing 2 deg at a time until there are no more power gains then back it off a bit.
Full Member
Joined: Nov 2003
Posts: 192
Likes: 8
From: .
I have to admit I haven't tried 48mm chokes but when 295rwhp is possible with 45mm chokes why would you? I think the biggest I would go is 46mm, any bigger than that and there really is not much 'shape' left.
If the float bowl is draining quickly a 3.3 needle and seat offers a substantial flow improvement over a 3.00.
If the float bowl is draining quickly a 3.3 needle and seat offers a substantial flow improvement over a 3.00.
I have to admit I haven't tried 48mm chokes but when 295rwhp is possible with 45mm chokes why would you? I think the biggest I would go is 46mm, any bigger than that and there really is not much 'shape' left.
If the float bowl is draining quickly a 3.3 needle and seat offers a substantial flow improvement over a 3.00.
If the float bowl is draining quickly a 3.3 needle and seat offers a substantial flow improvement over a 3.00.
Full Member
Joined: Nov 2003
Posts: 192
Likes: 8
From: .
Sorry, yes its a 13b PP engine. Flow is flow isn't it? I would have thought 'x' size choke would flow 'x' amount of air no matter what the porting configuration? I would be interested to know if there is more to it and why.
L - B9EGV, T - B10EGV. No amplifier, just a factory electronic distributor locked and set at about 22deg
L - B9EGV, T - B10EGV. No amplifier, just a factory electronic distributor locked and set at about 22deg
Rotary Freak
Joined: Dec 2006
Posts: 1,791
Likes: 0
From: New Hampshire
The same reasons why you don't put a 1200 cfm carb on a moped.
I have only been dealing with carbs for a short period of time but don't you want a balance between choke size (im guessing this is bore size) and power output? Mainly due to the throttle responce issue of using larger bore carbs?
Full Member
Joined: Aug 2004
Posts: 176
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From: NJ = PA
+
Well with my experience with PPs,turbo, NOS,alcohol(1/4-mile only!!) Webers up to 62mm carby and EFI .... it all boils down to Vol=efficiency - +CFM,vac,and internals weight,compression etc........ all depends on your goal and purpose for the engine to be?>> HI RPM ,mid range, endurance,turns,straight ,climing,etc., some times you have to lean them out to get that power,EFI is becoming popular less headaches, as for me WEBER ALL DA WAY!!!!!!!!!!!!!!!!!!!!!!!!!!!! 
PS Joe whats this build for ,road race , or 1/4mile? cheer's MECA
PS Joe whats this build for ,road race , or 1/4mile? cheer's MECA
Last edited by meca; Mar 30, 2008 at 02:28 PM.
