Lets discuss about Boosted Carbs on m20s

[dlguadiz]

I finally found an m20b25 that I can swap with my m20b20 for a 50+ boost in crank hp! Now on the other threads, I mentioned my goal is to get to around 200whp-250whp. Since I have a carb setup (Edelbrock, 600 cfm) like OLD MANs, I am fairly confident we can probably go to around 180+whp with better ignition/5-speed, differential upgrades.

Looking to push it some more. I have tried to see up to how much boost my stock 600cfm Carb can take without modding it for 'blow-through' and I came up with the following:

If with 4-5psi boost, Pr = (14.7+4)/14.7 = 18.7 / 14.7 = 1.27;

2.5 x 7800 x 100 VE x 1.27 / 5660 = 2476500/5660 = 437.50 CFM


In fact, with 10 psi boost, Pr Pr = 14.7 psi + 10 psi/ 14.7 psi = 1.68

2.5 x 7800 x 100 VE x 1.68 / 5660 = 3276000/5660 = 578.80 CFM


Well below the CFM rating of my Carb. If I can get to 200+ whp with only 4-5psi boost, I'd do it... if I could, I would like to avoid any intercoolers, etc. that would complicate things and add any 'point-of-failures'...

Currently looking at Eaton Superchargers or TVS Superchargers... because I don't want any turbo lag and is only looking for that extra boost on higher RPMs...

Thoughts? Sorry, no EFI for me as I am on a budget and would like to re-use whatever I have...

[Layne]

No one is going to discuss boosted carbs with you. The concept is completely dead. I've honestly never seen it done. If you must do it for whatever reason, you will do it alone with no help from the internet. You could easily work a job and buy a fuel injection system and have it installed and working well long before you'd ever get this idea off the ground.

[m60b30530i]

If you found a m20b25 then hopefully it came with the harness and associated fuel injection parts. It is only like 6 wires to run the bosch motronic computer. Plus you can add a inline pump or drop a walboro 255 in the tank for some extra fuel flow.

Also don't think of a inter cooler as a extra failure point. It cools the air entering the intake, cooler air = more hp.

[dlguadiz]

You could easily work a job and buy a fuel injection system and have it installed and working well long before you'd ever get this idea off the ground.

Sorry, but when I said "I'm on a budget..." that does not mean I am not capable of paying for an injection system. It just means I don't want to waste whatever money I already put on the carburetor system.

And I am actually partial to carbs. Why? Maybe I like tinkering with analog systems as a hobby because my day-time job requires me to develop digital control systems for machines (like EFIs and ECUs, etc.) -- if your dealing with computers all day long, you dont want to deal with computers as a hobby... ;>

No one is going to discuss boosted carbs with you. The concept is completely dead. I've honestly never seen it done. If you must do it for whatever reason, you will do it alone with no help from the internet.

There are tons of information on the internet and I've been reading them voraciously over the past couple of weeks. I just posted here as a sounding board just in case some of you guys have done it -- apparently not.

But you are correct. Maybe no one in this forum wants to discuss boosted carbs because the 320/6 is more prevalent in Europe than in the US... so there is really no base knowledge to work with. I'll just join the turbo and hot rod forums...

[dlguadiz]

Also don't think of a inter cooler as a extra failure point. It cools the air entering the intake, cooler air = more hp.

My target hp is around 200-250. The m20b25 engine is supposedly capable of around 170 hp -- at normal atmospheric pressure (14.7 psi). Over at the turbo forums, they say that a good rule of thumb to use is to assume that 14.7psi = 170 hp, and if you want to double that hp, to 340 hp, you have to provide an additional 14.7 psi. The relationship seems to be linear.

Applying math, 170 to 200 hp would require around 3psi, while 170 to 250 hp would require around 7 psi. So in terms of psi/boost, my goal is to provide around 3psi to 7psi.

The purpose of the intercooler from what I read, is that when you compress air using a turbo charger, the air gets hot from two sources -- (1) the turbo itself is run by the hot exhaust gases, and (2) the mere process of compression produces hot air. The first is part of the reason why I am planning on using superchargers instead. The second is not really a problem if I only resolve to get around 3-5psi compression -- its such a small amount that the temperature will probably not be adversely affected.

With that said, I'll probably start using an intercooler when I go past 5psi... as my computations above suggest, my 600 cfm carburator can probably take a max of 10psi (about 280 hp). At that hp however, the small differential will be the next problem...

[pofo]

Boost on a carb is not worth it in my book especially for 4-5 psi . They're very hard to tune correctly/safely for the increased boost pressure, plus you dont have any of the fail safes like a knock sensors that will save your motors life. There is no such thing as a cheap turbo build if you want it to last. I've been there several times and learned.

There is not much room on the front end for an intercooler but this is something that is needed in my book. The amount of heat the turbo creates you want to cool the air down as much as possible. Also they dont fail often.

IF I was you and on a budget I would do one of two things. 1 save more money and do it correctly. 2 sell all turbo parts and install a wet nitrous kit and call it a day.

[pommeree]

No one is going to discuss boosted carbs with you. The concept is completely dead. I've honestly never seen it done. If you must do it for whatever reason, you will do it alone with no help from the internet. You could easily work a job and buy a fuel injection system and have it installed and working well long before you'd ever get this idea off the ground.

I haven't been on the forums for a few years.
I've missed you Layne.
When I discovered I couldn't graft a '77 rear valence onto my '82 one of my first thoughts was, "Layne's going to give me so much sh-t for this."

[Layne]

I haven't been on the forums for a few years.
I've missed you Layne.
When I discovered I couldn't graft a '77 rear valence onto my '82 one of my first thoughts was, "Layne's going to give me so much sh-t for this."

Haha I actually found that really interesting. I always knew the part number was different, but they look the same. There's actually 3 or more different part numbers for the US tail panel (I think it's 3).