j9fd3s

iTrader: (3)

if you care about gas mileage or turn occasionally, look at wankel = awesome's list.

peejay

Or drivability... Or fuel economy... Or engine life...

MazdaMike02

iTrader: (4)

Yep I did. I already have jet extensions, race float bowls. I also have an adjustable vacuum diagphram. Like I said if it doesnt work out ill get rid of it. Lol and j9FD3S you posted some useful information in my thread as well. Mine is a 4 port TII 13B, 9.0:1 s5 TII rotors, and mine is a 600 cfm version.

Also nobody told me my carb was a piece of **** and get rid of it lol..but now you guys are changing your minds.

MazdaMike02

iTrader: (4)

Peejay. Its an RX7 im not that concerned about fuel economy, thats what my Mazda 3 is for lol. But I do want it to be reasonable. Engine life? Maybe if it floods all the time, but if thats the case ill just get an Edelbrock.

EDIT - Heres the link to my thread, has a lot of useful information. Most of the posters here posted in there too lol.

https://www.rx7club.com/showthread.php?t=1036321

peejay

Well, look at it this way. I have two registered cars, a VW and the RX-7. The VW hauls more and is winter-friendly but the RX-7 is more fun to drive. Careful tuning has the RX-7 getting better fuel economy.

So, proper tuning means I get to save money by driving the fun car and not the truck. Which is a large part of why the RX-7 got 11,000 miles on it in the last three months while the VW needs brakes all the way around because sitting has rusted them into blobs of violent pulsation.

And last time I had the header off, I had no visible carbon on the rotors aside from some light coloring in the as-cast part of the bowls.

j9fd3s

iTrader: (3)

ive tuned basically everything except a holley (webers, SU's, nikkis, all kinds of EFI, etc) and tuning is tuning, the engine wants (and you should listen to it), the fuel that it wants, and your job is to provide that. the airflow is dictated by the hardware

i don't particularly care what is used as a carb, as long as you can get it to deliver the fuel the engine wants anything will work.

the upsides to the holley are parts availability, and the 4 barrel should offer the ability to get good economy, with big power.

the downside is that since we mount it sideways, they don't like turns. they also are $$$ new for some reason.

wankel=awesome

!

Which led to:


I didnt say "They are pieces of **** and he should get rid of them!"

I said its not simply the jetting, and that this has been covered before, and is an expensive venue.

I also commented on the difference between getting a carb running and running right.

peejay

That's the funny thing, parts really aren't available for Holleys. You can replace the jets and diddle the idle mixture screw and get the accelerator pump all screwed up but that's it, most of the important things are non-adjustable, which is why they will make twelve different part numbers of X cfm carb, and you hope you're getting one that will work right with your engine.

That's where the aftermarket comes in, selling carbs that look like Holleys but are different in that they are expensive but actually work. Although some of them are expensive but don't work... my experience with a company that went out of business a while back (but whose name is now being slapped on to knockoff carbs made by an entirely different company) was fascinating - the carbs would drive like they were lean stumbling while all the time the engine would puff black soot and foul the plugs in a hundred miles. Must have had the worst atomization ever. This wasn't one carburetor but every one of that brand that I ever had the misfortune of working with, including a set of 3x2s. I had one 289 that ran 50 times better when I took off that junk and put a stock 3310 (750cfm) on it!

This is in stark contrast with Quick Fuel, which are the only carbs I've ever installed where they can go from the shipping box to the intake manifold and they don't need to be adjusted at all save for idle speed, and have razor sharp response and excellent drivabilty without resorting to running rich to compensate for poor calibration. They're not cheap, though.

When a GOOD carb is $1000-1200, it only makes sense to use a CRAP carb as an air metering device, and control fuel with a computer...

wankel=awesome

Hence my GSLSE with a 4bbl TB and injectors still in the factory location!

diabolical1

iTrader: (3)

here! here!

which is why after screwing around with my brother's Holley from i guess it must have been sometime in 1997 to sometime in 2006, i finally made the decision FOR HIM! EFI was the way to go and it would be based on the Holley manifold.

keep in mind the car went from a bucking, snorting, horrendously tempered with equally horrendous gas mileage (you could literally see the gauge move if you spent any time behind the wheel), to a very civil, even-tempered joy that got mileage in the low-to-mid 20s and still run neck-and-neck with an E36 M3 ... in ALL throttle conditions! the only remaining issue with it is the lack of a choke, so it is quite cold-blooded in the winter.

overall, i think we did a great job over the 9 years and when Megasquirt kicked my *** and we had to move the car back to storage, it was the good, ol' reliable Holley that we put back to work to do it.

the problem is i have no clue what was done to get it where it is ... because i did not collect data like i do now. the car spends A LOT of time in storage. he did some things to it and i did other things and we NEVER worked on it together or really communicated whatever changes we did make. so i can attest to a non-RB Holley being made to work, but i have no advice to give someone else and helpful advice with Holleys is pretty scarce around here which is why it baffles the hell out of me to see someone ask a question, then try to bite the head off one of the only people that can help significantly. frog and scorpion, i guess ....

j9fd3s

iTrader: (3)

when i'm tuning i use a notebook, to paraphrase, i don't have to remember. notebook goes in the glovebox, which is great if you have a glovebox...

diabolical1

iTrader: (3)

oh, no doubt on the notebook. i've been keeping one since ... hmm ... maybe 2003-04-ish. as a matter of fact, that one journal multiplied to about 5 or 6 now to keep the subjects separate. it's just that the noteworthy Holley stuff with my brother's car pre-dates 2003. i took his car to Florida (he's in New York) in 2006 to start the Megasquirt project on it and that's when i started a notebook on his car.

peejay

I have a special notebook that I keep for tuning... Really the bitch is the transition, there are a lot of things that interrelate (all Holleys are 4 corner idle, for example, but you can usually only adjust the primaries) so it's key to keep detailed notes on what you do and what the effects are.

Of course, tuning EFI, you just save after every tuning change, maybe write "before cruise tuning" in the filename because it's easy to forget what is what when you have 50 different tunes in your folder, but it's super easy to revert, especially in a system like MegaSquirt where if you accidentally do a bulk change to 10% instead of 110%, you can just exit and the change will be negated. That was a fun oopsie while tuning my first XFI system, finger slipped and I hit enter JUST as I saw that I only hit the 1 once, and by the way all tuning changes are automatically written to the computer so there IS no easy undo...

But I'm heartened that I'm not the only one who is EFI on a Holley manifold.

RotaryEvolution

iTrader: (30)

not all, the marine 2 barrels(500cfm) are just basically half a 4 barrel with larger throats. you also only really have 1 angle to starve the carb with but also half the adjustability factor to get it just right. they're also close to half the cost, but not quite as easy to find used.

peejay

Gotta be careful. 2 barrel Holleys are measured at a 4" vacuum across the carb, while four-barrels are measured at 2". Or something like that.

The point is, if you look at the specs, that "500cfm" Holley 2-barrel has the same venturi size and throttle plate size as my "750"cfm four-barrel.

So in 4-barrel measurements, it's roughly 375cfm.

That's why I prefer to think of it in terms of the actual sizes involved. My 750 is four 42mm throttle plates with 35mm primary chokes and 36.5mm secondary chokes. When you compare it to people running a pair of 45DCOEs with 38mm chokes, it doesn't really look that big anymore, does it?

edit: Found a cheat sheet. The 500cfm 2300 has 1 3/4" throttles and 1 9/16" chokes. So that is 44.5mm throttle and 40mm chokes. I stand corrected, it's not half a 750 like I'd remembered. It does still seem small for a rotary not running a plenum under the carb though.

j9fd3s

iTrader: (3)

and 2" of vacuum over the carb is rather a lot. this is one of the reasons a 465cfm carb works on a 300cfm engine

peejay

There has to be some depression, though, or else air wouldn't flow through it.

I wonder what Cup cars were doing a little while ago. 900hp through a 390cfm carb. They ran really high compression and odd ignition timing to compensate, the only problem being that they had to be careful with the throttle at lower RPM.