A/F Ratios and Air Restrictions
#1
A/F Ratios and Air Restrictions
Hello all, this is my second post, but I've lurked for a while now, and I even used the magic search button. I just got my 90 miata with BEGi Shanghai turbo/ megasquirt PNP/Intercooled, dyno'd. The tuner maxed out my stock injectors and made 158 HP 169 lb/ft at 10 psi. After talking to both FM and BEGi they both think that is dreadfully low, and BEGi thinks it might be a restriction in the air flow. I was running rich (around 11-13 A/F) for about 8/9 months before I could tune it. I may have fried my cat; I won't know I can take it off and look (Sunday afternoon).
My question is since the tuner tuned it with that (potential) restriction what will happen if I 1: Gut the cat for the mean time, 2: Replace it with a new working/non blocked cat?
My question is since the tuner tuned it with that (potential) restriction what will happen if I 1: Gut the cat for the mean time, 2: Replace it with a new working/non blocked cat?
#3
Tour de Franzia
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I had this same problem and peaked at 180whp. I then installed a Walbro 255 and now it will make over 300whp.
It sounds to me like you've been running at 13:1 AFR which means your ---- is burnt.
It sounds to me like you've been running at 13:1 AFR which means your ---- is burnt.
#4
Well if you are adding all the fuel to get the right ratio and just not making the power with it I would say you are lacking in the spark advance or engine compression department. If you're not getting all the power you should while getting the same air flow and fuel then there is something happening in the combo chamber that isnt up to snuff.
#5
I was running the base map for 8 months, but I had it tuned at Church's Dyno in LA, CA.
Well if you are adding all the fuel to get the right ratio and just not making the power with it I would say you are lacking in the spark advance or engine compression department. If you're not getting all the power you should while getting the same air flow and fuel then there is something happening in the combo chamber that isnt up to snuff.
I won't have time until Sunday afternoon to take the cat off and see if it is toast. If it isn't anyone know how to check for restrictions in the cat back? I have a Borala dual exhaust.
#7
Tour de Franzia
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Those numbers don't seem right. I thought Stoichiometric for gas was 14.7 A/F
I was running the base map for 8 months, but I had it tuned at Church's Dyno in LA, CA.
Which ---- is burnt??? The cat? Something in the engine?? Also I was told (by Flyin Miata) that the stock pump is usually good for something like 250whp. Maybe I misunderstood? I will be ordering either 550 Injectors from BEGi or 700 Injectors from Flyin Miata on Monday. Any one here tried either on a Megasquirt PNP??
I was running the base map for 8 months, but I had it tuned at Church's Dyno in LA, CA.
Which ---- is burnt??? The cat? Something in the engine?? Also I was told (by Flyin Miata) that the stock pump is usually good for something like 250whp. Maybe I misunderstood? I will be ordering either 550 Injectors from BEGi or 700 Injectors from Flyin Miata on Monday. Any one here tried either on a Megasquirt PNP??
I'll help you out since you're new:
- buy EV14 injectors if you're going to spend the money, but you need to convert to sequential fuel. If you aren't going to convert to sequential fuel, then you're pretty-much stuck running ---- injectors.
- many people say the stock fuel pump is fine, mine was not. The pump is 23-years old, changing it isn't the worst idea I've ever heard.
- Yes, we all use those injector sizes. I have 550cc EV1s in my car and they work but kind of suck compared to the level of awesome that is modern fuel injectors.
#8
Stoich is 14.7, but awesome chemical properties and laws of physics push us to make peak output around 11.5:1 in most scenarios. Running at 14.7:1 in boost will create too much heat for steel valves, most pistons, and most rings. Fancy, modern engines with exotic metals can run stoich in boost at reasonable power levels, we can't. You have a 30-year old engine design, welcome to vintage racing.
I'll help you out since you're new:
I'll help you out since you're new:
- buy EV14 injectors if you're going to spend the money, but you need to convert to sequential fuel. If you aren't going to convert to sequential fuel, then you're pretty-much stuck running ---- injectors.
- many people say the stock fuel pump is fine, mine was not. The pump is 23-years old, changing it isn't the worst idea I've ever heard.
- Yes, we all use those injector sizes. I have 550cc EV1s in my car and they work but kind of suck compared to the level of awesome that is modern fuel injectors.
#16
Do you have a link for TSE? I don't know this distributor. I found these but don't know if they are correct: Fuel Injector Clinic injectors - MiataRoadster - High-performance customer service...and parts for Roadsters
#17
Do you have a link for TSE? I don't know this distributor. I found these but don't know if they are correct: Fuel Injector Clinic injectors - MiataRoadster - High-performance customer service...and parts for Roadsters
injector dynamic is prob the best.
#18
Tour de Franzia
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Do you have a link for TSE? I don't know this distributor. I found these but don't know if they are correct: Fuel Injector Clinic injectors - MiataRoadster - High-performance customer service...and parts for Roadsters
I think TSE does the 750cc injectors cheaper, and they're Injector Dynamics instead of Chinese or whatever. Isn't Miata Roadster guy is the guy who left this forum because of me?
Aren't you still on batch-fuel?
#19
Trackspeed Engineering
I think TSE does the 750cc injectors cheaper, and they're Injector Dynamics instead of Chinese or whatever. Isn't Miata Roadster guy is the guy who left this forum because of me?
Aren't you still on batch-fuel?
I think TSE does the 750cc injectors cheaper, and they're Injector Dynamics instead of Chinese or whatever. Isn't Miata Roadster guy is the guy who left this forum because of me?
Aren't you still on batch-fuel?