LocostUSA.com

Learning how to build Lotus Seven replicas...together!
It is currently November 21, 2018, 1:48 am

All times are UTC - 5 hours [ DST ]




Post new topic Reply to topic  [ 22 posts ]  Go to page 1, 2  Next
Author Message
PostPosted: December 25, 2007, 3:21 pm 
Offline
User avatar

Joined: August 4, 2007, 5:43 pm
Posts: 196
Location: SF
I posted this in the electrical section but then thought this was more appropriate, sorry about that - mods, you can remove the other thread if you want.

Has anyone done a carb conversion on a 1.8 miata engine? We're trying to do away with the insanely large wiring harness and thought it might be neat to run an old school setup. Possibly also a distributor if we can. If not carb and distributer, then we'll do a carb conversion and run an aftermarket ignition system.

If anyone has done either both conversions or just a carb conversion with an aftermarket ignition system and can give us some direction, it would be awesome.

Thanks,
217.

_________________
Project 217 - Started 8/4/07 Build Thread Here!


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: December 27, 2007, 8:25 pm 
It's been done a few times, mostly by people in Japan.

The first question is why. You'll never get a carb setup to work as well as a good fuel injection setup, although some people are more comfortable working with carbs because they're easier to understand. On a Miata, there's no good reason to pull the fuel injection or the distributorless ignition. On a Locost, there's a bit more reason although it will (ironically) cost you more money.

For mounting the carbs, use the same adapters that people are using for homebrew individual throttle body setups. I have one from Boig Motorsports, but they're more expensive than some others. TWM can probably help out as well. Regardless of source, they'll typically have a Weber flange on the end.

For a distributor, that's easy. Mazda (and Ford, and Kia) used a dizzy on longitudinal applications. It plugs right in to the Miata head where the cam angle sensor is now. Then you'll have managed to downgrade your modern fuel and ignition system to the same level of sophistication as my 1960's Land Rover :wink:


Top
  
Reply with quote  
 Post subject:
PostPosted: December 27, 2007, 8:59 pm 
Offline
User avatar

Joined: September 10, 2006, 11:29 pm
Posts: 380
Keith Tanner wrote:
It's been done a few times, mostly by people in Japan.


It's been done a number of time - but rarely for street cars. SCCA Production cars required carbs until recently.

Do a search on clubroadster.net for a couple carb conversions. IIRC, there was at least one on miata.net also.


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: December 27, 2007, 9:27 pm 
Of course, E Production cars. I forgot about that, although that's why Boig Motorsports sells the adapter that's on my desk. F Production Miatas run fuel injection and DIS though.


Top
  
Reply with quote  
PostPosted: September 16, 2017, 12:11 am 
Offline
User avatar

Joined: November 11, 2013, 4:47 am
Posts: 963
Location: No. Nevada
Yah, I know, resurrecting the dead. :ack:
This thread came up when I began searching for a Weber manifold to fit a Miata 1.8.

Glad to find it but strongly disagree that going to Webers and a distributor is throwing anything away except unnecessary complication.
Actually I think I can keep the distributor-less ignition fairly easily.
But that oversize and overly complex FI needs to go away for my intended use.

Tried to search BOIG Motorsports but all I found there were Cobra clone parts.
So still trying to locate a Weber intake.
Might be able to mill one from billet but it may be expensive to get the CAD done.

_________________
If I must be a one-man PC free zone, so be it!


Top
 Profile  
Reply with quote  
PostPosted: September 16, 2017, 12:21 pm 
Offline

Joined: January 27, 2010, 1:11 pm
Posts: 412
Location: Jefferson City, MO
If you still want to go carb maybe get one of the itb manifolds they sell and get four individual bike carbs.

_________________
Build on

Chris
Build: NA Miata based +221 Se7en


Top
 Profile  
Reply with quote  
PostPosted: September 18, 2017, 4:11 pm 
Offline
User avatar

Joined: July 4, 2006, 5:40 pm
Posts: 1927
Location: Novato, CA
I wouldn't mill one, but I might try welding one, like a typical British intake manifold. A flat flange could be water-jet cut from 3/16 or 1/4" sheet. Weld on four short pipes, a transverse tube connecting the pipes, then a carburetor flange (or two) onto that.


Top
 Profile  
Reply with quote  
PostPosted: September 20, 2017, 9:15 pm 
Offline

Joined: November 27, 2013, 11:44 pm
Posts: 27
I am currently doing this very same thing, but on a 1.6. I am using 40 DCOE's and my plan is to keep the stock ECU to run the ignition only. I was lucky enough to find a Mazdaspeed manifold on EBAY (p/n 0000-06-5301) which greatly simplified things. I have a book called Mazda Miata Performance Handbook, by Norman H. Garrett III, in which he explains a way to "trick" the ECU into thinking it still sees an AFM or MAF in the case of the 1.8. If I cant get that to work Ill do a megajolt. He also gives a base line for jets and chokes. Im going to start with his suggestions and see what happens.


Top
 Profile  
Reply with quote  
PostPosted: September 20, 2017, 9:32 pm 
Offline
User avatar

Joined: November 11, 2013, 4:47 am
Posts: 963
Location: No. Nevada
Thanks for the tip, all I found were pics of TWM but no current listing.

_________________
If I must be a one-man PC free zone, so be it!


Top
 Profile  
Reply with quote  
PostPosted: October 28, 2018, 5:19 pm 
Offline

Joined: November 27, 2013, 11:44 pm
Posts: 27
mckwrench wrote:
I am currently doing this very same thing, but on a 1.6. I am using 40 DCOE's and my plan is to keep the stock ECU to run the ignition only. I was lucky enough to find a Mazdaspeed manifold on EBAY (p/n 0000-06-5301) which greatly simplified things. I have a book called Mazda Miata Performance Handbook, by Norman H. Garrett III, in which he explains a way to "trick" the ECU into thinking it still sees an AFM or MAF in the case of the 1.8. If I cant get that to work Ill do a megajolt. He also gives a base line for jets and chokes. Im going to start with his suggestions and see what happens.



Two weeks ago I started this set-up for the first time and it ran like a top. Fired on the first turn of the crank. The idle speed and mixture were even almost-close. I used the stock Miata ECU and stripped everything out of the harness that isn't needed to run the ignition. I built the "black box" from Norm Garretts book to flip the signal from a MAP sensor. If anyone is interested I will post the detail of the ECU wiring. Now I need to shift my focus eleswhere so I can start to tune at other-than-idle.


Top
 Profile  
Reply with quote  
PostPosted: October 29, 2018, 3:52 pm 
Offline
User avatar

Joined: May 27, 2006, 9:46 pm
Posts: 1883
Location: BC, Canada. eh?
https://danstengineering.co.uk/index.ph ... uct_id=627

They're out there, now.

_________________
Scratch building, at continental-drift speed, a custom McSoreley-design framed, dual-Weber 45DCOE carburated, Zetec-engined, ridiculously fast money pit.

http://zetec7.webs.com/


Top
 Profile  
Reply with quote  
PostPosted: October 29, 2018, 6:23 pm 
Offline
Automotive Encyclopedia
User avatar

Joined: December 22, 2006, 2:05 pm
Posts: 5793
mckwrench wrote:
mckwrench wrote:
I am currently doing this very same thing, but on a 1.6. I am using 40 DCOE's and my plan is to keep the stock ECU to run the ignition only. I was lucky enough to find a Mazdaspeed manifold on EBAY (p/n 0000-06-5301) which greatly simplified things. I have a book called Mazda Miata Performance Handbook, by Norman H. Garrett III, in which he explains a way to "trick" the ECU into thinking it still sees an AFM or MAF in the case of the 1.8. If I cant get that to work Ill do a megajolt. He also gives a base line for jets and chokes. Im going to start with his suggestions and see what happens.



Two weeks ago I started this set-up for the first time and it ran like a top. Fired on the first turn of the crank. The idle speed and mixture were even almost-close. I used the stock Miata ECU and stripped everything out of the harness that isn't needed to run the ignition. I built the "black box" from Norm Garretts book to flip the signal from a MAP sensor. If anyone is interested I will post the detail of the ECU wiring. Now I need to shift my focus eleswhere so I can start to tune at other-than-idle.


How about some pics of your work? Where did you get the circuit components? Do your carbs have the parts Norman suggested?
The 89 or so 323 turbo distributor should fit also. It has fly weights and vac advance. I saw Norman fit SU carbs too.

_________________
MV8

https://www.youtube.com/watch?v=Om3C1Ep ... D3E18BB447


Top
 Profile  
Reply with quote  
PostPosted: October 29, 2018, 8:58 pm 
Offline

Joined: November 27, 2013, 11:44 pm
Posts: 27
MiataV8, sure. This is the mess I started with:
The entire harness from a ‘91 Miata. I got it running and everything worked. I wanted to have a solid baseline for the timing, to eliminate at least one variable


Attachments:
92EB9481-A8C7-4443-B3CD-A9A24111FF82.jpeg
92EB9481-A8C7-4443-B3CD-A9A24111FF82.jpeg [ 1.61 MiB | Viewed 590 times ]
9000B0B0-5EE7-46AF-98A8-E33AA9885EC5.png
9000B0B0-5EE7-46AF-98A8-E33AA9885EC5.png [ 745 KiB | Viewed 590 times ]
Top
 Profile  
Reply with quote  
PostPosted: October 29, 2018, 9:07 pm 
Offline

Joined: November 27, 2013, 11:44 pm
Posts: 27
After many hours of studying Miata wiring diagrams and troubleshooting books I figured out what I knew I needed, what I might need and what I definitely didn’t need. Then I just started cutting. In the end there are only 9 wires left at the ECU. The rest of the bundle is for lights, switches and gauges.


Attachments:
B1D17E4D-A3AF-4DE2-9F03-5FB1E5CF4DA8.png
B1D17E4D-A3AF-4DE2-9F03-5FB1E5CF4DA8.png [ 1.65 MiB | Viewed 590 times ]


Last edited by mckwrench on October 29, 2018, 9:12 pm, edited 1 time in total.
Top
 Profile  
Reply with quote  
PostPosted: October 29, 2018, 9:10 pm 
Offline
User avatar

Joined: November 11, 2013, 4:47 am
Posts: 963
Location: No. Nevada
Tell us more!
Exactly WHICH nine? :D
Schematic?

_________________
If I must be a one-man PC free zone, so be it!


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 22 posts ]  Go to page 1, 2  Next

All times are UTC - 5 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 2 guests


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 post attachments in this forum

Search for:
Jump to:  
POWERED_BY