RotaryEngineIllustrated.com Forum Index RotaryEngineIllustrated.com
This site endeavors to be the best resource on the internet for educational material on the Rotary Engine.
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

HELP

 
Post new topic   Reply to topic    RotaryEngineIllustrated.com Forum Index -> The Round Table
View previous topic :: View next topic  
Author Message
TITO



Joined: 09 Aug 2005
Posts: 31
Location: Brampton Ontario Canada

PostPosted: Tue Aug 09, 2005 6:45 pm    Post subject: HELP Reply with quote

Hello I recently got my hands on a 1985 Rx-7 GSL. It is nothing fancy, no turbo, or SE, but i got it dirt cheap and the boddy is almost perfect.

Anyhow, my car has some carberator problem I think. It is runnig rough and groggy, and whenthe choke cuts so does the engine. I am wondering if any one elce had this problem before, and how they solved it, and if it is actualy the carb?

Now I also wondering what little things can I do to teh car to increase HP for as little cost as posible? The ideal hp range would be in teh 200hp range, but this is probly not fesable in my price range, and ablities lol.

thanks.
_________________
Only he is truly lost when he gives himself up for lost
Back to top
View user's profile Send private message Send e-mail MSN Messenger
Blake
Been there, done that


Joined: 12 Jul 2005
Posts: 135
Location: Portland, OR

PostPosted: Tue Aug 09, 2005 11:54 pm    Post subject: Re: HELP Reply with quote

TITO wrote:
Hello I recently got my hands on a 1985 Rx-7 GSL. It is nothing fancy, no turbo, or SE, but i got it dirt cheap and the boddy is almost perfect.

Anyhow, my car has some carberator problem I think. It is runnig rough and groggy, and whenthe choke cuts so does the engine. I am wondering if any one elce had this problem before, and how they solved it, and if it is actualy the carb?


Hard to say, from your description. You might want to start by checking for vacuum leaks, then go from there.

Quote:
Now I also wondering what little things can I do to teh car to increase HP for as little cost as posible? The ideal hp range would be in teh 200hp range, but this is probly not fesable in my price range, and ablities lol.


200 hp is not remotely plausible for a non-turbo, un-ported 12A, no matter what the budget. Stock HP was right around 100. You can get about a 30% gain, simply from doing the exhaust. The best setup is from Racing Beat, but their complete systems can be costly (though, you get what you pay for). A more budget option is to get a downpipe/presilencer setup from Rotary Performance (aka RX7.COM). Much cheaper but more modest gains. Intake is not such a big deal, until you really start pushing things. Of course, there are big gains to be had by rebuilding and porting the motor. Are you dealing with emissions?
_________________
Blake Qualley
Pineapple Racing, Inc.
(503) 233-3878
Back to top
View user's profile Send private message Send e-mail Visit poster's website
TITO



Joined: 09 Aug 2005
Posts: 31
Location: Brampton Ontario Canada

PostPosted: Wed Aug 10, 2005 8:26 pm    Post subject: Reply with quote

I live in canada so any car 20 years and older does not have to go through emission testing.

Eventauly I would like to rally the car, if that makes a differnece.

Now I know this is a dumb question but how do these exhasut systems improve hp? ( I am just getting into mechanics, but I do know the jist of things)
_________________
Only he is truly lost when he gives himself up for lost
Back to top
View user's profile Send private message Send e-mail MSN Messenger
Blake
Been there, done that


Joined: 12 Jul 2005
Posts: 135
Location: Portland, OR

PostPosted: Wed Aug 10, 2005 9:45 pm    Post subject: Reply with quote

Quote:
Now I know this is a dumb question but how do these exhasut systems improve hp? ( I am just getting into mechanics, but I do know the jist of things)


Not a dumb question...it all comes down to Volumetric Efficiency (VE). VE is how much of the theoretical displacement is actually utilized. The more air/fuel mixture (A/F) goes in, the more power you can produce. Not only do you need to make it easy for the A/F to get to the chamber, the chamber needs to be as empty as possible to make room for it. Reducing exhaust backpressure, improving exhaust flow and even synchronizing the exhaust pulses to the port timing are all elements to improving VE and, thus, power production.

Rotary engines respond particularly well to exhaust improvements, comparred to piston engines. Piston engines use valves and their induction and exhaust tracts typically have sharp bends in them. Rotary engines have big ports and the tracts are very direct. It is not uncommon to see power gains of 30% just by opening up the exhaust.
_________________
Blake Qualley
Pineapple Racing, Inc.
(503) 233-3878
Back to top
View user's profile Send private message Send e-mail Visit poster's website
TITO



Joined: 09 Aug 2005
Posts: 31
Location: Brampton Ontario Canada

PostPosted: Thu Aug 11, 2005 7:27 pm    Post subject: Reply with quote

ic ic. I was reading on the 12A engine, and I understand it does not have ECU, nor does it use back presure to assist in the sealing of porst, unlike the 13B that does.

This lead me to thinking if i just cut off teh exhaust, so there is no catalytic converters, no muflers, and run a straight pipe system out the side of the car just above and behind the wheel front wheel well, it would maximse hp?????

thanks
_________________
Only he is truly lost when he gives himself up for lost
Back to top
View user's profile Send private message Send e-mail MSN Messenger
TITO



Joined: 09 Aug 2005
Posts: 31
Location: Brampton Ontario Canada

PostPosted: Fri Aug 12, 2005 7:05 pm    Post subject: Reply with quote

I gues i am completly out to lunch lol
_________________
Only he is truly lost when he gives himself up for lost
Back to top
View user's profile Send private message Send e-mail MSN Messenger
Blake
Been there, done that


Joined: 12 Jul 2005
Posts: 135
Location: Portland, OR

PostPosted: Mon Aug 15, 2005 1:37 pm    Post subject: Reply with quote

It's a common misconception that the shortest exhaust is "ideal", but that is not true for rotary engines. Experience shows that you actually want the longest possible exhaust for the best power. Think of the exhaust as a series of pressure pulses. Every time the exhaust ports open, they shoot a high pressure stream of exhaust into the system. When the ports close, the pressure drops. These pressure pulses have momentum (energy) and march down the exhaust like a freight train. That freight train actually creates 'negative' pressure pulses that, when syncronized correctly, actually help suck the exhaust out of the engine and give the intake charge a head-start on filling the chamber. This is called scavenging. A long exhaust can scavenge better due to the freight train effect. Of course, it takes some experimentation with exhaust length to get it just right, but generally longer is better.
_________________
Blake Qualley
Pineapple Racing, Inc.
(503) 233-3878
Back to top
View user's profile Send private message Send e-mail Visit poster's website
TITO



Joined: 09 Aug 2005
Posts: 31
Location: Brampton Ontario Canada

PostPosted: Mon Aug 15, 2005 8:11 pm    Post subject: Reply with quote

OUt of curiosity what would u say the optimum length is?
_________________
Only he is truly lost when he gives himself up for lost
Back to top
View user's profile Send private message Send e-mail MSN Messenger
TITO



Joined: 09 Aug 2005
Posts: 31
Location: Brampton Ontario Canada

PostPosted: Mon Aug 15, 2005 8:18 pm    Post subject: Reply with quote

i have another question here. My car has a strange Idle issue. It usualy idle realtivly high, often times above 3000 RPMs. What is going on? I doubt that is normal.
_________________
Only he is truly lost when he gives himself up for lost
Back to top
View user's profile Send private message Send e-mail MSN Messenger
GTChris



Joined: 13 Jul 2005
Posts: 13
Location: Portland, OR.

PostPosted: Tue Aug 16, 2005 8:04 am    Post subject: Reply with quote

Does it only rev high when cold? Or intermitantly?
Back to top
View user's profile Send private message Visit poster's website AIM Address Yahoo Messenger MSN Messenger
TITO



Joined: 09 Aug 2005
Posts: 31
Location: Brampton Ontario Canada

PostPosted: Tue Aug 16, 2005 1:58 pm    Post subject: Reply with quote

It would rev high wheni first start it, and teh car only runs for about 5 minuts ( i need a new carberator).

I solved the problem though.... reading the manual always helps lol.

thanks for all the help
_________________
Only he is truly lost when he gives himself up for lost
Back to top
View user's profile Send private message Send e-mail MSN Messenger
enthusiast



Joined: 07 Sep 2005
Posts: 4
Location: sydney

PostPosted: Wed Sep 07, 2005 6:23 am    Post subject: Re: HELP Reply with quote

TITO wrote:


Now I also wondering what little things can I do to teh car to increase HP for as little cost as posible? The ideal hp range would be in teh 200hp range, but this is probly not fesable in my price range, and ablities lol.

thanks.


u can have your carby modified for bout 20 bucks !!!
i reckon an extra 10 hp or so..what u reckon blake ?
_________________
Rx7...was Black S1 with white simons and fat sticky rears..black interior with red here n their
had a equalizer amp and sub when sold to car dealer...anyone seen it around ??
Back to top
View user's profile Send private message
Arawn



Joined: 06 Nov 2005
Posts: 11
Location: Bridgeport, Conn

PostPosted: Sun Nov 06, 2005 12:06 pm    Post subject: Tuning Exhaust Reply with quote

TITO wrote:
OUt of curiosity what would u say the optimum length is?

At a first guess, Frequency times Speed of Sound, for that mix and temperature.

You might also try half the Speed of Sound, as the explosive exit should send a wave of Vaccuum back to the exhaust port.

What's your RPM? Could your machine shop build you a Trombone?

Arawn
_________________
In the Love, and Dysdeign, of the Works of the Hand, Moderation in Moderation.
Back to top
View user's profile Send private message Send e-mail
Blake
Been there, done that


Joined: 12 Jul 2005
Posts: 135
Location: Portland, OR

PostPosted: Mon Nov 07, 2005 10:33 pm    Post subject: Reply with quote

The optimal length is a very tricky thing that requires experimentation to get right. On my peripheral port 13B with 2-inch primaries, we found 66 inches to be a very good collector length. Half of that (33") would also likely work. But no matter how good your guessing is, the test is to build the entire exhaust, run the car at a given RPM, wipe an oily rag over the length and observe the light and dark rings, indicating low and high pressure standing waves. You want low pressure at the exhaust port face and high pressure inside the mufflers and at the tip of the tail pipe. And if you move just one thing, all those points may change. Smile
_________________
Blake Qualley
Pineapple Racing, Inc.
(503) 233-3878
Back to top
View user's profile Send private message Send e-mail Visit poster's website
TITO



Joined: 09 Aug 2005
Posts: 31
Location: Brampton Ontario Canada

PostPosted: Wed Nov 09, 2005 1:16 pm    Post subject: Reply with quote

maybe i won't touch anything then. better safe then sorry
_________________
Only he is truly lost when he gives himself up for lost
Back to top
View user's profile Send private message Send e-mail MSN Messenger
Display posts from previous:   
Post new topic   Reply to topic    RotaryEngineIllustrated.com Forum Index -> The Round Table All times are GMT - 7 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group