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Is 12psi boost on pump gas possible
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earlesurfs
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PostPosted: Thu May 31, 2012 6:38 pm    Post subject: Is 12psi boost on pump gas possible Reply with quote

I am eventually going to turbo efi my car. I have an AEM box and a friend that worked for AEM that will teach me the tuning procedures with this system.

I currently have a 2287 with around 240-245 HP normaly aspirated. I have ported super flow heads and 12.5:1 compression.
I would like to lower the compression to around 8.5 or 9:1. I will have my wiesco pistons dished and maybe get the chambers massaged for lower comp. if I cannot reach the desired comp. I will have to replace the heads.

I am running a fk-46 cam and it seems pretty good. I would like the same cam but on 114 lobe centers. Any advice you could give me on this?

So a 2387 flanged crank, pauter rods, wiesco pistons, fk-46 on 114 lc and ported super flows on 12 psi boost. Will it run on pump gas?

What kind of horse power should I expect from this combination? I know there are many variations but a rough estimate would be cool.

Thanks in advance for any input

Earle
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MURZI
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PostPosted: Thu May 31, 2012 7:16 pm    Post subject: Reply with quote

My buddy runs 18-20 psi with superflo's and Pantera EFI.....it's all about timing and fuel control. My guess is he is making 330 plus......Pump gas, driven daily.......
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Last edited by MURZI on Thu May 31, 2012 7:59 pm; edited 1 time in total
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Juanito84
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PostPosted: Thu May 31, 2012 7:46 pm    Post subject: Reply with quote

The lower the compression ratio, the lower the VE (volumentric efficiency, i.e. high RPM cam), the later the spark, the greater the amount of fuel (or water)and the better the quench all make higher boosts possible.

There comes a point when gasoline spontaneously combusts. This is called, among other things, detonation, pinging, knocking, compression ignintion, all depending mainly when and to what extent it happens. As air is squeezed into a small space it heats up.

The turbo does some comression but some of that heat, not all, can be released by the intercooler.

The compression stroke also compresses, but how much depends on the compression ratio, when the intake valve closes, how good the rings are, etc. With the right cam design even 100 PSI would be possible. (Look up miller cycle)

Ignition also causes compression because ignition almost always starts before top dead center. As the gas expands it puts more pressure on the remaining fuel and air so therefore a spark too soon creates pinging. Fully adjusted timing (intitial, total, RPM curve, LOAD curve, etc.), especially hand in hand with a knock sensor that automatically retards timing in case of pinging is best.

Fuel (or some other liquid like water or alchohol) also cools the air as it vaporizes under the heat and pressure. That's why carburetors have power jets and fuel injection systems also enrich the mixture at WOT (wide-open-throttle). This is because at WOT there is more pressure in the cylinder. With boost even more added fuel (or other liquid) could increase the effect even more. (Look up water injection for forced induction)

Quench is when the piston is designed to come very close to the head. This makes the air in that area squirt into the combustion chamber which can swirl the air and fuel around past the valves instead of letting it sit stagnent on the hot exhaust valve. Quench also allows the spark to be set off later since it causes the fuel to burn quicker which also contributes to the prevention of detonation.

Obviously the other anti-knock factor is higher octane. In most areas there are different gasolines of different octanes. So you could gain some benifit of using high octane pump gas.
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modok
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PostPosted: Thu May 31, 2012 7:53 pm    Post subject: Reply with quote

it is possible..........but
WTF would you risk hurting an engine like that running 12 PSI on pump gas?

penny wise pound foolish
Keep it down to 8 psi on pump, start mixing in race gas above that, keep a margin of safety so you don't ruin your 8 thousand dollars worth of parts
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miniman82
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PostPosted: Thu May 31, 2012 8:12 pm    Post subject: Reply with quote

Why do people always ruin N/A race engines by trying to turbo them? Rolling Eyes

Build it turbo from the beginning, don't build a bastard.
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DarthWeber
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PostPosted: Thu May 31, 2012 8:21 pm    Post subject: Reply with quote

miniman82 wrote:
Build it turbo from the beginning, don't build a bastard.
VWracerdave couldn't have said it better! Laughing
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Swapped the Compufire for a Bosch blue and some points I had sitting around, started 1st crank. Took her out for a drive, pulls harder, more RPM, and runs smoother. I think I'll be sticking with points from now on.

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MURZI
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PostPosted: Thu May 31, 2012 8:24 pm    Post subject: Reply with quote

miniman82 wrote:
Why do people always ruin N/A race engines by trying to turbo them? Rolling Eyes

Build it turbo from the beginning, don't build a bastard.


I think the common situation is .....you build a beast and then you get bored..... I know the feeling....saving for my wedgemated crank...and TURBEAUX
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turbodon1776
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PostPosted: Thu May 31, 2012 11:55 pm    Post subject: Reply with quote

i made 490 with a set of superflows and fk87 on 112lc .. 2276cc

building a bastard... pff these guys are living in a dream world.

you can build it however you want and probably decimate anyone who has posted in this thread so far.

112+ lobe is a good idea for the vacuum signal on your efi. cams are a touchy subject everyone has an opinion on whats works best. there are big cam guys and little cam guys. my advise.. take advise from someone with a proven track record.. kawell, lummus, crawford and so on... (all big cam guys BTW)

the baron used to run a set of flycut superflows with .250 deck to get into the 9s a while ago. but you know that would be a bastard combo Rolling Eyes
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turbodon1776
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PostPosted: Fri Jun 01, 2012 12:13 am    Post subject: Reply with quote

Here are some pics of my Super Flows. for the 490horse powerplant 46x40 valves and k800 springs
it takes a good amount of welding to be able to open them up enough to flow. without welding they're no better than a vw casting wedgeport.
Also in my application (draw thru) an IDF style manifold welded and match ported with a plenum on top of it kept flow numbers up with no bottlenecking of restrictive "endcastings"
Image may have been reduced in size. Click image to view fullscreen.

Image may have been reduced in size. Click image to view fullscreen.

Image may have been reduced in size. Click image to view fullscreen.

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Donald Michaelson

had a bad ass car but it has departed

2276 Turbo motor
fk87
superflo heads
490HP
9.56 ET

now I clunk around in a 65 baja bug
Chevy Ecotec Engine
091 trans
coilovers, bypasses and all the fun $tuff
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earlesurfs
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PostPosted: Fri Jun 01, 2012 3:54 am    Post subject: Reply with quote

miniman82 wrote:
Why do people always ruin N/A race engines by trying to turbo them? Rolling Eyes

Build it turbo from the beginning, don't build a bastard.


I am planning on taking it completely apart and starting over when I finally do the turbo build. If I need to change any parts I will.


Thanks for all the input. I have built over a dozen fast N/A engines. I'm just trying to figure out what is possible and what to expect when going turbo.

My ultimate goal is a car that is capable of driving to Fontana, running some low 10 second passes then drive it home. (probably won't ever do This Though. I figure I could accomplish this with around 350-375 HP. I will be running an intercooler and possibly meth/water injection. I was just wondering if i could do this on pump gas.

Thanks for all the input.
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Boolean
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PostPosted: Fri Jun 01, 2012 5:08 am    Post subject: Reply with quote

Yes you can, but it will of course be easier with better fuel.
If ignition and fuel is correctly mapped (I figure you are using FI and programmable ignition.) it will be safe and easy. Using someones recommendation on timing rather than benchtesting your engine you'd be better off with the best fuel money can buy.
Note that "safe" is relative...
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Ejbbal21
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PostPosted: Fri Jun 01, 2012 4:17 pm    Post subject: Reply with quote

I have a 2332 that I run 15 pounds of boost. I built it with 7 to 1 compression. I'm blowing through dual 45 dellorto's with the hottest cam cb has for turbo motors and some conservative 044 heads. Also With high lift rockers. I run pump gas in the Phoenix AZ heat and no pinging. I have a msd BTM and distro to control the timming. Btw it's in a baja with a 091 bus Trans and 33X10.5 BFG mud tires. I have been told that I'm in the 250hp range to the ground considering the tires I have.

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67Beetle2017
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PostPosted: Fri Jun 01, 2012 4:56 pm    Post subject: Reply with quote

I agree that you can detune your 12.5:1 engine and recam for turbo.

I have personally run 14psi on the street with premium fuel.

It was a 1914 with ported 42X37.5 Performance Tech stage 7 heads 48mm dellorto side draft, with a CB turbo cam. The car was very fast on the street with no detonation. Again this was in the early 90's so with today's technology in ignition and fuel management, you should be able to run 12psi with success. NOTE: this 1915 engine was built with .050" deck and 7.0:1 compression.

I can attest to running in the 9's with .200"+ deck. Back in 1992 I built a 2275 with heavily massaged superflo's, Kawell cam, and .200 deck. Compression was 7.5:1 with 24psi. We ran a 9.42 then a 9.66 in 112°F weather. So it can be done but I am sure there are better ways to go about it. Dynoed at 486HP.

If I could do the 2275 over again I would raise compression to about 9.0:1 and get the deck closer to .050".
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earlesurfs
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PostPosted: Sat Jun 02, 2012 8:57 am    Post subject: Reply with quote

Awesome! Thanks for all the comments, advice and stories.

Earle
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Bassplayer247
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PostPosted: Thu Jul 18, 2013 9:59 am    Post subject: Reply with quote

modok wrote:
it is possible..........but
WTF would you risk hurting an engine like that running 12 PSI on pump gas?

penny wise pound foolish
Keep it down to 8 psi on pump, start mixing in race gas above that, keep a margin of safety so you don't ruin your 8 thousand dollars worth of parts


Modok has a point, however, I believe that if you get your tune perfect, running 12psi is possible on an aircooled VW that is intercooled running pump gas. You have to run it really rich and retarded at that pressure though.

It would be a shame to blow up your engine whilst trying to perfect the tune for 12psi though.
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Juanito84
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PostPosted: Thu Jul 18, 2013 3:41 pm    Post subject: Reply with quote

Dual ignition would help reach that goal too.
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Muffler Mike
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PostPosted: Thu Jul 18, 2013 4:14 pm    Post subject: Reply with quote

in my opinion, boost number shoud not be the ultimate yard stick on what one can get away with on pump gas, i think it sould be bases on ve and hp
a perfect example from my experience. my car weighs in at 1950 lbs. my guestamate s around 330hp at the flywheel to run my 10.60 index. my stuff has always been far from perfect but i am not heads up racing so i didnt spend the time to make it better. it worked and was consistent. i finally bit the bullet and switched to methanol. took about 18 lbs to run the 10.60 range. same boost as gas for 10.90 index. exactly what i wanted to accomplis at the time. needless to say i found a slight problem with manifold, instead of fixing, i made all new. now the only change was manifold and to run 10.60 now only takes 7-8 lbs. if i put it back on race gas, my best guess is it drops back to around 300 hp or so. can pump gas handle making 300 hp even though its only 7 lbs? i dont know. i have increased the amount of air/fuel going into the cylinder, thus increasing the dynamic compression. witch is one of the enemies to fuel that has the wrong octane. although less boost is less heat generated, so that would be a big plus. would be a cool experiment that's for sure. lot of things to try with cam timing, chamber shapes, piston top shape, ignition timing etc.
hell just run e-85. it comes out of the pump. or just use methanol. bigger tuning window and only $5 a gallon. although it will fell more like $10 a gal.
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