Dual Carbs vs FI vs FI+Turbo for Power AND Drivability

Dual Carbs vs FI vs FI+Turbo for Power AND Drivability

Joined: June 18th, 2008, 2:29 am

June 28th, 2008, 5:27 pm #1

Hey all, I'm always reading the website with interest on what everyone has/can do with their x's and a lot of ingenuity, and am curious on what type of power and drivability differences folks have seen by tweaking the existing engine/transmission setup.

For instance I inherited dual carbs on my 77x with 1.5 liter transplant with a Serra big valve head and I believe a Serra cam also and it feels a LOT spunkier (and louder ) then a FI 1985 I considered and drove. In fact the 85 was in great shape and while it started right up and idled perfectly (something my X is still challenged with as I learn about idle mixtures) it was so slow and anemic that I almost bagged my quest of owning an X until I found and drove my current car 6 months ago. I was amazed how much stronger the dual carb car felt in comparison. How much is from the carbs versus the head/cam ?

I figure my car must have at least 85-90 horses based on seat of my pants meter. If I did replace the carbs with FI, does it need to be adjusted for the serra head/cam setup ? This also sounds counterintuitive but would I LOSE power and go back down closer to the 75 stock horsepower with fi ? I assume fi system is logical step if I ever wanted to attempt a turbo system that Damonfg has, should I do anything different when getting fi system if I wasn't sure about adding turbo but wanted to keep options open ? How much extra juice can an aftermarket turbo add ?

I'll prob keep the dual carbs for awhile since they're fun to listen to but also if I can get the chokes and idle setup so drivability isn't such an issue, but can't help from daydreaming about turning my vintage X into more of a rocket! My stock engine cover went to the paint shop today and will be ready in a week!

thanks !
Jeff
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Eric Hamilton (Durham NC)
Eric Hamilton (Durham NC)

June 29th, 2008, 1:16 am #2

Properly set up FI just about has to beat carbs, especially across varying operating conditions. The whole idea is to get the exact right ratio of fuel and air, and a closed-loop FI system measures what's actually happening in the cylinders to adjust that ratio. By comparison, a carb is a bundle of compromises - every jet, every calibrated orifice is the exact right size for one particular combination of ambient temperature, RPM, altitude, throttle opening, and less than perfect for all other conditions.

But I still like playing with webers




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Joined: August 22nd, 2005, 3:13 am

June 29th, 2008, 2:40 am #3

altho i like to play with my grill more than the carbs.. but the sound of the carbs are just so awesome... i couldnt imagine an FI X


X addict/masochist
Probablly the ONLY honda tech that drives a fiat
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Joined: May 21st, 2002, 4:25 am

June 29th, 2008, 4:48 am #4

Hey all, I'm always reading the website with interest on what everyone has/can do with their x's and a lot of ingenuity, and am curious on what type of power and drivability differences folks have seen by tweaking the existing engine/transmission setup.

For instance I inherited dual carbs on my 77x with 1.5 liter transplant with a Serra big valve head and I believe a Serra cam also and it feels a LOT spunkier (and louder ) then a FI 1985 I considered and drove. In fact the 85 was in great shape and while it started right up and idled perfectly (something my X is still challenged with as I learn about idle mixtures) it was so slow and anemic that I almost bagged my quest of owning an X until I found and drove my current car 6 months ago. I was amazed how much stronger the dual carb car felt in comparison. How much is from the carbs versus the head/cam ?

I figure my car must have at least 85-90 horses based on seat of my pants meter. If I did replace the carbs with FI, does it need to be adjusted for the serra head/cam setup ? This also sounds counterintuitive but would I LOSE power and go back down closer to the 75 stock horsepower with fi ? I assume fi system is logical step if I ever wanted to attempt a turbo system that Damonfg has, should I do anything different when getting fi system if I wasn't sure about adding turbo but wanted to keep options open ? How much extra juice can an aftermarket turbo add ?

I'll prob keep the dual carbs for awhile since they're fun to listen to but also if I can get the chokes and idle setup so drivability isn't such an issue, but can't help from daydreaming about turning my vintage X into more of a rocket! My stock engine cover went to the paint shop today and will be ready in a week!

thanks !
Jeff
an 85,depending on what options the 85 has.(Look at the test weights in the old road tests) The cammed and dual carbed car is probably peakier too(the power comes on with a rush)compared to the FI that has a smoother torque curve.That can throw your "seat of the pants dyno" off a lot.Also,how well tuned an example is can really change the feel,I've done basic tuneups on slow feeling X's that changed the entire feel of the car.
Last edited by clasicalgas on June 30th, 2008, 3:27 am, edited 1 time in total.
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Joined: December 21st, 2004, 3:04 am

June 29th, 2008, 7:01 am #5

Hey all, I'm always reading the website with interest on what everyone has/can do with their x's and a lot of ingenuity, and am curious on what type of power and drivability differences folks have seen by tweaking the existing engine/transmission setup.

For instance I inherited dual carbs on my 77x with 1.5 liter transplant with a Serra big valve head and I believe a Serra cam also and it feels a LOT spunkier (and louder ) then a FI 1985 I considered and drove. In fact the 85 was in great shape and while it started right up and idled perfectly (something my X is still challenged with as I learn about idle mixtures) it was so slow and anemic that I almost bagged my quest of owning an X until I found and drove my current car 6 months ago. I was amazed how much stronger the dual carb car felt in comparison. How much is from the carbs versus the head/cam ?

I figure my car must have at least 85-90 horses based on seat of my pants meter. If I did replace the carbs with FI, does it need to be adjusted for the serra head/cam setup ? This also sounds counterintuitive but would I LOSE power and go back down closer to the 75 stock horsepower with fi ? I assume fi system is logical step if I ever wanted to attempt a turbo system that Damonfg has, should I do anything different when getting fi system if I wasn't sure about adding turbo but wanted to keep options open ? How much extra juice can an aftermarket turbo add ?

I'll prob keep the dual carbs for awhile since they're fun to listen to but also if I can get the chokes and idle setup so drivability isn't such an issue, but can't help from daydreaming about turning my vintage X into more of a rocket! My stock engine cover went to the paint shop today and will be ready in a week!

thanks !
Jeff
... a STOCK FI set up... but a "Dedicated Port" FI setup will outperform the carbs, given the same head, valves, and cam.

Then... there are Turbos and Blowers...

A Stock FI can be made to outperform the carbs also with heads, and a cam, and headers...

For the street though, any FI is really the only way... the Carbs are really made for all out and wide open stuff, and get pretty difficult in traffic.

BUT... they SOUND and LOOK so COOL!

Your choice Jeff... Have fun!


My best,



Tony
Black Tooth and me... since 1983!
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Joined: April 17th, 2002, 1:56 pm

June 29th, 2008, 1:16 pm #6

Hey all, I'm always reading the website with interest on what everyone has/can do with their x's and a lot of ingenuity, and am curious on what type of power and drivability differences folks have seen by tweaking the existing engine/transmission setup.

For instance I inherited dual carbs on my 77x with 1.5 liter transplant with a Serra big valve head and I believe a Serra cam also and it feels a LOT spunkier (and louder ) then a FI 1985 I considered and drove. In fact the 85 was in great shape and while it started right up and idled perfectly (something my X is still challenged with as I learn about idle mixtures) it was so slow and anemic that I almost bagged my quest of owning an X until I found and drove my current car 6 months ago. I was amazed how much stronger the dual carb car felt in comparison. How much is from the carbs versus the head/cam ?

I figure my car must have at least 85-90 horses based on seat of my pants meter. If I did replace the carbs with FI, does it need to be adjusted for the serra head/cam setup ? This also sounds counterintuitive but would I LOSE power and go back down closer to the 75 stock horsepower with fi ? I assume fi system is logical step if I ever wanted to attempt a turbo system that Damonfg has, should I do anything different when getting fi system if I wasn't sure about adding turbo but wanted to keep options open ? How much extra juice can an aftermarket turbo add ?

I'll prob keep the dual carbs for awhile since they're fun to listen to but also if I can get the chokes and idle setup so drivability isn't such an issue, but can't help from daydreaming about turning my vintage X into more of a rocket! My stock engine cover went to the paint shop today and will be ready in a week!

thanks !
Jeff
Carl and I did some tests on his 124 switching between carbs (dual 40IDF) and stock FI. There was no real difference in numbers. The carbs sounded and felt faster, but the figures showed barely any difference. Granted the 40s are a little small for a 2l, but it gives you an idea. If you are considering turbo, start with a whole new engine, since carbs, cams and compression are the opposite of what you need for turbo. If it were up to me, I'd leave the engine as is and enjoy the dual carbs.

Good luck



Erwin Timmers '87 Bertone
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Joined: June 18th, 2008, 2:29 am

June 29th, 2008, 2:40 pm #7

Hey all, I'm always reading the website with interest on what everyone has/can do with their x's and a lot of ingenuity, and am curious on what type of power and drivability differences folks have seen by tweaking the existing engine/transmission setup.

For instance I inherited dual carbs on my 77x with 1.5 liter transplant with a Serra big valve head and I believe a Serra cam also and it feels a LOT spunkier (and louder ) then a FI 1985 I considered and drove. In fact the 85 was in great shape and while it started right up and idled perfectly (something my X is still challenged with as I learn about idle mixtures) it was so slow and anemic that I almost bagged my quest of owning an X until I found and drove my current car 6 months ago. I was amazed how much stronger the dual carb car felt in comparison. How much is from the carbs versus the head/cam ?

I figure my car must have at least 85-90 horses based on seat of my pants meter. If I did replace the carbs with FI, does it need to be adjusted for the serra head/cam setup ? This also sounds counterintuitive but would I LOSE power and go back down closer to the 75 stock horsepower with fi ? I assume fi system is logical step if I ever wanted to attempt a turbo system that Damonfg has, should I do anything different when getting fi system if I wasn't sure about adding turbo but wanted to keep options open ? How much extra juice can an aftermarket turbo add ?

I'll prob keep the dual carbs for awhile since they're fun to listen to but also if I can get the chokes and idle setup so drivability isn't such an issue, but can't help from daydreaming about turning my vintage X into more of a rocket! My stock engine cover went to the paint shop today and will be ready in a week!

thanks !
Jeff
I think using the chokes will help a lot. I have a small choke control not connected to anything installed in between the 2 seats at about handbrake level, and need to construct a guide for the cable to not bind on anything.

thanks, Jeff
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Joined: September 25th, 2004, 5:43 am

June 29th, 2008, 11:17 pm #8

That's the ticket Jeff. One FI, one dual carb. Problem solved.

If there are any other problems nagging at you, just say the word. My ability to spend your money, to solve these problems, is boundless.

jd


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        1978                1986  \
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2005 FFO Photo Gallery
Last edited by JimDecker on June 29th, 2008, 11:17 pm, edited 1 time in total.
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Joined: June 18th, 2008, 2:29 am

July 1st, 2008, 2:54 pm #9

The X looks to cool sitting next to my mr2 turbo...I wonder how much that car storage lift (someone on the forum has shown pics) costs ?
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Joined: September 25th, 2004, 5:43 am

July 2nd, 2008, 5:19 am #10

if you consider around $2K "not that much".

Check this one out.

jd


Code: Select all

        1978                1986  \
[/b]
2005 FFO Photo Gallery
Last edited by JimDecker on July 2nd, 2008, 5:20 am, edited 1 time in total.
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