How to get to a 150 hp 12A?
Apprentice Guru
Joined: Oct 2001
Posts: 1,425
Likes: 0
From: Cloud Nine and Peak of God
Sometimes I think there are too many posts about performance not born out by dyno data or track times.
"my car was off that day but when its really tuned and I get a great launch I will get high 14s'!
When I start looking for actual evidence the best I can get is a 150 hp 1984 GSL will get to 0-60mph in 7.6 seconds and pass through the 1/4 trap in 15.6 seconds. Reducing weight significantly and optimal launch and gear changes with luck will get the car down to around 15.2-15.3 seconds. Still waiting for a dyno and track slip which shows anything different.
My daily driver. a Nissan Skyline without mods, can do the 1/4 in 13 seconds flat. So Gen 1 RX-7s have a long way to go before I buy one just for performance!
"my car was off that day but when its really tuned and I get a great launch I will get high 14s'!
When I start looking for actual evidence the best I can get is a 150 hp 1984 GSL will get to 0-60mph in 7.6 seconds and pass through the 1/4 trap in 15.6 seconds. Reducing weight significantly and optimal launch and gear changes with luck will get the car down to around 15.2-15.3 seconds. Still waiting for a dyno and track slip which shows anything different.
My daily driver. a Nissan Skyline without mods, can do the 1/4 in 13 seconds flat. So Gen 1 RX-7s have a long way to go before I buy one just for performance!
Old [Sch|F]ool
Joined: May 2001
Posts: 12,866
Likes: 573
From: Cleveland, Ohio, USA
My math shows that it takes 105hp to make a 2600lb car do a 1/4mi in 17.0 seconds and 80mph. This coincides very neatly with a '79 RX-7 as-tested by practically all magazines I have reviews for. (Screw it if I end a sentence with a preposition!)
That same math also says that if a car weighing 2400lb travels the 1/4mi in 15.1 seconds at 90mph, it is making 130hp.
I would not doubt that if the car was brought down to 2400lb as it goes down the track, 150hp can result in 14-second timeslips. If the car weighs 2750lb (stock GSL with average driver), then it can still do mid-15's.
That same math also says that if a car weighing 2400lb travels the 1/4mi in 15.1 seconds at 90mph, it is making 130hp.
I would not doubt that if the car was brought down to 2400lb as it goes down the track, 150hp can result in 14-second timeslips. If the car weighs 2750lb (stock GSL with average driver), then it can still do mid-15's.
Full Member
Joined: Jan 2025
Posts: 58
Likes: 4
From: Palm Coast, FL
the whole thread is about NON-ported 12a and how to get 150hp.
the subject comes up plenty of times in this forum. Like said the magic number is 150hp, I am sold on this theory which I did not come up with just what I have read here and elsewhere and I think is dead on accurate.
mid 14s with a non ported 12a n/a in a first gen (FA or FB) is not easy to achieve <---summarizing what is been described here, that includes any STOCK port being japanese, european, US, etc blocks.
My formula 150hp (I think
)if anybody cares:
engine:
45DCOE weber lake city intake
Carter 7 psi fuel pump
Holley FPR
Yaw advanced timing
Magnecore 10mm ignition cables/stock coils
header/ 2.5" no presilencer/dynomax superturbo muffler
electric fan
no pwr steering
non-horsepower acceleration/reliability/drivability improvers...
weight redux(no rear anything, including bins)
Peejay's cable engine brace
rear drums
no a/c (finally decided to get rid of it)
old style oil cooler
fuel and a/f meter gauges
dual alt pulley
stock clutch disc
modified pressure plate
215/50/13s all around
still NOwhere in low 15s (too many cars running flat 15s that can beat mine and I ain't a bad driver)...much less 14s, come porting should be well on low 14s with a large streetport
the subject comes up plenty of times in this forum. Like said the magic number is 150hp, I am sold on this theory which I did not come up with just what I have read here and elsewhere and I think is dead on accurate.
mid 14s with a non ported 12a n/a in a first gen (FA or FB) is not easy to achieve <---summarizing what is been described here, that includes any STOCK port being japanese, european, US, etc blocks.
My formula 150hp (I think
)if anybody cares:engine:
45DCOE weber lake city intake
Carter 7 psi fuel pump
Holley FPR
Yaw advanced timing
Magnecore 10mm ignition cables/stock coils
header/ 2.5" no presilencer/dynomax superturbo muffler
electric fan
no pwr steering
non-horsepower acceleration/reliability/drivability improvers...
weight redux(no rear anything, including bins)
Peejay's cable engine brace
rear drums
no a/c (finally decided to get rid of it)
old style oil cooler
fuel and a/f meter gauges
dual alt pulley
stock clutch disc
modified pressure plate
215/50/13s all around
still NOwhere in low 15s (too many cars running flat 15s that can beat mine and I ain't a bad driver)...much less 14s, come porting should be well on low 14s with a large streetport
this list of mods almost is what Ill be running here shortly.I have a stockport 12a GS
I recently acquired a full RB road race exhaust system, a weber 45DCOE and intake, and a fuel pressure regulator. I have gaskets, O-rings, and an OMP block off plate/gasket on the way for install here soon.
-What jets and such did you run on your Weber45?
-Do you absolutely need to run a new fuel pump, will the stock one work for a stockport motor?
-Timing, is it necessary to change this and how do you do it properly? I see cut 2 marks on the main drive pulley.
On the Weber currently, this is what I know about the jet sizes:
40mm chokes
f11 emulsion tubes
65F9 Idel Jets
.090 Pump Jets
180 Main Jets
175 Air Jets
Im just diving into this carb and Im trying to absorb info and read up on this. Im still unsure on cause and effect for changing jets out and how to actually understand (ah this is happening so I will change out X-jet for Y-jet).
Any help is appreciated, Thanks
Tried stock fuel pump on my OER 45 (a "race" version of weber 45DCOE) and ran out of fuel in the bowls in 5th. Granted this was with the stock fuel pump, probably original.
Jets, I ordered what I was told and then went 2 sizes both directions. I went with a F7 e-tube though, your results may vary.
Jets, I ordered what I was told and then went 2 sizes both directions. I went with a F7 e-tube though, your results may vary.
You will need better fuel flow but the pressure will still need to be low for webers/dellortos/nikkis. I use a Carter 4070 with a regulator set to 2.5 psi. You will also need a better ignition system, look up DFIS in various forms. Doing an electric fan setup and reducing the load on the alternator by relaying your fuel pump and headlights will also help. You will probably need a new clutch if it still has an old OEM one, the extra oompf will probably wear it out. Timing can be set aggressively since detonation is not a concern since not boosted. Play with it until you get the best results.
in addition to everything said directly above me (t_g_farrell), check these out:
https://www.racingbeat.com/mazda/per...or-tuning.html
https://www.racingbeat.com/mazda/per...ps/timing.html
there's a lot more info out here (on this board) that you can learn from, but i started with the RB catalog. i guess they don't sell the actual book any more, but those links give a condensed version of what they had in the old catalog/tech manual.
https://www.racingbeat.com/mazda/per...or-tuning.html
https://www.racingbeat.com/mazda/per...ps/timing.html
there's a lot more info out here (on this board) that you can learn from, but i started with the RB catalog. i guess they don't sell the actual book any more, but those links give a condensed version of what they had in the old catalog/tech manual.
Full Member
Joined: Jan 2025
Posts: 58
Likes: 4
From: Palm Coast, FL
You will need better fuel flow but the pressure will still need to be low for webers/dellortos/nikkis. I use a Carter 4070 with a regulator set to 2.5 psi. You will also need a better ignition system, look up DFIS in various forms. Doing an electric fan setup and reducing the load on the alternator by relaying your fuel pump and headlights will also help. You will probably need a new clutch if it still has an old OEM one, the extra oompf will probably wear it out. Timing can be set aggressively since detonation is not a concern since not boosted. Play with it until you get the best results.
Full Member
Joined: Jan 2025
Posts: 58
Likes: 4
From: Palm Coast, FL
in addition to everything said directly above me (t_g_farrell), check these out:
https://www.racingbeat.com/mazda/per...or-tuning.html
https://www.racingbeat.com/mazda/per...ps/timing.html
there's a lot more info out here (on this board) that you can learn from, but i started with the RB catalog. i guess they don't sell the actual book any more, but those links give a condensed version of what they had in the old catalog/tech manual.
https://www.racingbeat.com/mazda/per...or-tuning.html
https://www.racingbeat.com/mazda/per...ps/timing.html
there's a lot more info out here (on this board) that you can learn from, but i started with the RB catalog. i guess they don't sell the actual book any more, but those links give a condensed version of what they had in the old catalog/tech manual.
I'm running a cheapo Airtex or some other stock equivalent pump on a 12A street port with a 45 DCOE and there's still enough fuel to blip for the downshift.
Could have been because your pump was old like you say.
It's great that zombie threads can still provide useful info.
I remember threads from the time saying the stock pump was barely able to feed a stock 12A, yet Datsun guys like to get our pumps for their triple Weber conversions.
Full Member
Joined: Jan 2025
Posts: 58
Likes: 4
From: Palm Coast, FL
You will need better fuel flow but the pressure will still need to be low for webers/dellortos/nikkis. I use a Carter 4070 with a regulator set to 2.5 psi. You will also need a better ignition system, look up DFIS in various forms. Doing an electric fan setup and reducing the load on the alternator by relaying your fuel pump and headlights will also help. You will probably need a new clutch if it still has an old OEM one, the extra oompf will probably wear it out. Timing can be set aggressively since detonation is not a concern since not boosted. Play with it until you get the best results.
Ok so I went with a Carter 4594, it was a few bucks cheaper then the 4070 on Summit for some reason. I have a Summit 1-4.5psi regulator and liquid low pressure gauge. My car is an 85 GS so it dosent have the points system, but I did NGK all around and MSD blasters (8222) that’s about all I can do right now for ignition. New higher output alternator is on the way. Pretty much following what you’ve all done in the past. Thanks again!
Where was this at? The back straight at Circuit of the Americas is 1 km/.6 mi and it's over 5000 rpm in 4th before I have to brake for the next corner.
I'm running a cheapo Airtex or some other stock equivalent pump on a 12A street port with a 45 DCOE and there's still enough fuel to blip for the downshift.
Could have been because your pump was old like you say.
It's great that zombie threads can still provide useful info.
I remember threads from the time saying the stock pump was barely able to feed a stock 12A, yet Datsun guys like to get our pumps for their triple Weber conversions.
I'm running a cheapo Airtex or some other stock equivalent pump on a 12A street port with a 45 DCOE and there's still enough fuel to blip for the downshift.
Could have been because your pump was old like you say.
It's great that zombie threads can still provide useful info.
I remember threads from the time saying the stock pump was barely able to feed a stock 12A, yet Datsun guys like to get our pumps for their triple Weber conversions.
I’ve driven a couple of stock fuel pump/modified Nikki cars that all ran out of fuel at the top of 3rd if doing a good launch and WOT.
