Whats wrong with this turbo setup?

Propane, Butane, LPG, GPL, C3H8, C4H10
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dayzedandkonfuzed
Posts: 10
Joined: Wed May 28, 2014 1:12 am

Whats wrong with this turbo setup?

Post by dayzedandkonfuzed » Sat Feb 10, 2018 8:19 pm

First off, I'd like to say that this forum is so great that I rarely have to post anything because I find the answers I'm looking for.

So I've spent a reasonable amount of money on parts and plumbing, and I've suddenly been made aware of an issue with my turbo setup. So I would like to lay it all out here and get some advice on how to proceed, before I do something I need to reverse.

I have a Chev 454, bone stock, 8:1 compression. I'm doing a blow thru with an OHG 450. Space is a big issue. I'd like to run up to 10psi. I have no "hp goal." I've just found out that my model E converter is only good up to about 330hp. While this may be enough for 5 psi, it's not going to be enough when I crank up the boost later down the line. The questions I know to ask now: Do OHG mixers have a hp rating? If so, how much would my 450 be good for? If I can get away with 1 mixer, is there anything wrong with teeing 2 converters to it? Will I need 2 lockoffs? If I need 2 mixers, do you think they could be plumbed in series? (<---That seems like a dumb question but I can't figure out why not.) How much power can be made with a standard -6 feed line from the tank? Am I overthinking this? (lol)

Thanks in advance!


storm
Posts: 560
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: Whats wrong with this turbo setup?

Post by storm » Sun Feb 11, 2018 5:07 am

In general terms on a naturally aspirated engine you need 1.5 cfm/hp so a carb that flows 450 cfm should (when all else is equal) be able to flow enough air to help produce 300 hp. Forced Induction is just a matter of doing some more maths.

For fuel flow take a look at the link in my signature. I know nothing about sizes when it comes to dash lines. We simply don't use lines like that in Australia for LPG as they are not certified here for LPG use. In my experience the biggest restriction (in fuel flow) is the electric lock offs. On a single lock off tank a 10mm (or 3/8") LPG line can flow more than the lock off.
Every job is a self-portrait of the person who did it. Autograph your work with excellence.

Fuel flow requirements calculations viewtopic.php?f=5&t=1638

gottago
Posts: 200
Joined: Thu May 24, 2012 7:39 pm
Location: British Columbia Canada

Re: Whats wrong with this turbo setup?

Post by gottago » Mon Feb 12, 2018 1:02 pm

You are asking most all the right questions dayzed. The ohg is good for a few more hp than the impco but probably only up around 360. I've teed two converters in series to one mixer before. No diff really but that was with both running off one lockoff. I'd go with the single/single setup and see how you like it. There is a 20 second or so burst of fuel when you go wot that seems to surpass the hp restrictions. Then you are just running off whatever the biggest choke point you have. Likely the lockoff. Gives you a base point to see how far you want to go to get more. Its only money after this but it just might surprise you what it will do with the simple single/ single setup. Its a big block!

dayzedandkonfuzed
Posts: 10
Joined: Wed May 28, 2014 1:12 am

Re: Whats wrong with this turbo setup?

Post by dayzedandkonfuzed » Tue Feb 13, 2018 2:37 am

gottago wrote:
Mon Feb 12, 2018 1:02 pm
Its only money after this but it just might surprise you what it will do with the simple single/ single setup. Its a big block!
By single/ single you mean just 1 converter and 1 mixer? If I can get away with that for now and add later I might go that route. It's just a street car after all.

gottago
Posts: 200
Joined: Thu May 24, 2012 7:39 pm
Location: British Columbia Canada

Re: Whats wrong with this turbo setup?

Post by gottago » Tue Feb 13, 2018 12:47 pm

Its a good starting point imo, cheapest and easiest way to get it going and see what it does. One ohg 450 with one x1 converter gives you a bit more than a single impco setup. Work out the bugs and modify from there if need be.

burbfixer
Posts: 15
Joined: Mon Nov 06, 2017 10:07 am

Re: Whats wrong with this turbo setup?

Post by burbfixer » Sun Feb 18, 2018 12:11 pm

dayzed,
This sounds like a great project! Propane + boost is a great combo and you will no doubt be pleased with the results. And I agree with gottago, you've asked good questions.

+1 on the idea of starting with a single mixer/converter setup and seeing where you are at. I doubt you will be disappointed with the way it runs, even at 10 PSI boost. What you will likely experience is that at some rpm the mixture will go lean and power will flatten out, and you will want to upshift. But below that rpm, torque will likely be amazing! The converter will likely be the first restriction, then lockoff. A wideband O2 setup would be helpful in knowing exactly what your mixtures are doing. If by 2 mixers in series, you mean 'stacking' them somehow in air tube between the turbo and throttle body, I doubt it would be worth the effort. If it worked at all, it would likely run way too rich at lower rpm's, and you do not want that....

Tank pressure is what determines how much fuel flows thru a -6 liquid line. That will be the least of your concerns unless you are operating at full throttle on extremely cold days. When I worked in the industry, part of my job was tuning fuel mixtures out on the highway. It had to be extreme cold weather before there was any fuel starvation issues. A stock vortec 454 would go lean at full throttle on a -40 day, but I never remember any issues in temps warmer than that. A single -6 liquid line should feed a very high horsepower engine in normal day to day temperatures.

Not trying to be a know-it-all, and you didn't specifically ask about these things, but a couple of other important things come to mind with a combo such as yours, so I thought I'd mention them just in case....
You said it's a bone stock engine. If that means it's a well used engine that hasn't been apart and at least cleaned, carbon buildup could cause it to detonate and/or backfire under boost. I would recommend at least pulling the heads to clean the chambers and piston tops, and installing new head gaskets. This would be cheap insurance. Feed the turbo cool air, keep engine temps in the 170-180 range, make sure there is full coolant flow through the converter, and make sure the converter is 'boost referenced' with a balance line.

Also, before you fire this thing and go for your first ride, make sure your ignition system is in very, very good condition. A performance aftermarket system such as an msd would be ideal, but at a bare minimum, use new, good quality cap, rotor, wires, and coil. Propane demands more of an ignition system even on a stock engine, and boost adds even more demand. I suggest using 1 heat range cooler plugs, and gap them down a bit. No more than .035. Actually, .030 might be safer initially. What you are trying to avoid is lean backfires, so give your ignition system every advantage you can, and you should be fine, even if the mixtures go a bit lean on you momentarily while you are testing it out.

Have fun, and please share the results once you get it up and running!

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