First off, this is my first post on this forum, so please go easy on me.

I have a land speed racing bike that I run on the Bonneville Salt flats.
It has set a record NA but I am really considering upping my game with a turbo.

the bike is a GL1000
The book says it's 80 hp. stock.
Since it's running at 6000 ft. density altitude I figure my fastest engine getting probably 75 hp. up there.
I'd like to get that up to around 120 hp.
maybe 6 - 8 lbs. boost.

I have a couple of different engines with different specs and I'm researching what combination to put together.
I'm really just concerned with WFO performance.

First Question:
I have both 31 mm. and 32 mm. carburetors
could I use the 31 mm. carbs with a bit more boost and get the same results?

This turbo stuff is all new to me, I'm doing it all myself with just the internet for direction, so there will probably be many stupid questions.
Thanks

 

Yes defiantly Turbo it! It really dosent matter what size carb your using when the difference is so small until you are deciding on some final tune aspects with various minimal carb difference sizes. Also that small carb sizing difference really makes no difference at all in power output. Try to run 8psi.

 

What's the engines displacement and the rpms when it makes the 80hp?

6,000' is 11.77psi atmospheric pressure, or 11.77÷14.7=80%, 80hp×80%=65hp. So you need +20% density increase just to get sea level power, or +87% to get to your 120hp goal. You'll be more around the 16lbs of boost area.

 

Thanks for the replies.
The DA on the salt varies pretty much between 5000 and 7000 ft. depending on on the time of day.
I picked 6000 ft. as it is the mid point.

According to what I have seen, HP loss is 3% per 1000 ft. elevation gain so I was figuring 18% loss
at 6000 ft. Pretty close to the 20% that you have calculated.

Word on the salt is that it takes about 3 psi. boost just to bring the engine back to sea level HP numbers.

My engines are 1975 - 1979 Honda Gl 1000 goldwing engines.
There are basically 2 different engines in this lineup.
Same bottom ends, different carbs and cams.

Early engine:
1000 cc. - 80 hp. @ 7500 rpm.
Later engine:
1000 cc. - 78 hp. @ 7000 rpm.

I've been messing with the online calculators and have seen the VE of .74 for the bigger carb engine
and .77 for the smaller.

I don't know if the engine can handle 16 lbs. without spitting out a head gasket, which is why I
have been focusing on more conservative boost numbers.

Any info that you guys can provide to point me in the right direction is much appreciated.

 

Been there - done that with the speed wobble.
The chassis in the racing bike is a GL1100.
It has a bigger front end, bracing, better suspension and a 3" longer wheelbase than the GL1000's.
The bike is pretty stable at 134 on the salt, now I want to make it go fast.

 

1,000cc is 61cu/in, spin it to 7500rpms and that's 132cfm. Corrected that's 10lbs/min, good enough for 100hp. Engine makes 80, so that's 80% ve.

Since we know we're going to lose 20% from elevation, we have to "overshoot" the power goal. Your 120hp goal is really 150hp at sea level, which we know is 15lbs/min. In order to shove 15lbs/min, boost needs to be 13.6psi in the manifold. Accounting for 2psi lost going through an intercooler, that's 15.6psi at the turbo outlet, which is important to factor when your looking at compressor maps.

16psi at sea level is a 2.08 pressure ratio, but because your at lower atmospheric pressure, the turbo will be running at 2.36, so look for a turbo with peak efficiency around 2.36 pressure ratio and 15lbs/min.

Garrett GBC14 looks like a good fit, https://www.garrettmotion.com/racin...alog/turbo/garrett-boost-club-line-gbc14-200/

 

Wow, thanks bbi !

Your post contains more useful information than I have been able to find in the last 2 months of casual searching of the net.

It appears that I may have to adjust my goals.
I just don't know if my engine will handle 16lbs. I'm pretty confident that my carbs can't.

Being a typical broke racer , I can't justify grenading my stuff just to find out what the limit is.

I have tried the Garrett boost advisor a couple of times and have always gotten a " contact your local dealer" response.
I didn't even know that they made the GBC14 turbos.

 

I don't know anything about those engines so I can't offer any advice on that. I would think someone, somewhere, has experience force feeding one of those.

What about converting it to efi with a megasquirt?

 

Another question if you don't mind:

Since the original arbitrary goal of 120 hp. seems too optimistic for my engine,
How can I go about calculating a realistic hp. number using lower boost amounts?

Example:
If I have 10 lbs. coming out of the compressor housing, lose 2 psi. in the intercooler,
have 8 lbs. in the plenum, How much hp. can I expect to gain?

I don't know how to do that math.
At 60, it's getting harder for this old dog to learn new tricks.

Is there a good on line calculator that you guys recommend?

I really think that I'm going to have to keep the boost numbers low to keep from hurting my engine,
I can always turn it up later.

 

That's actually pretty easy, power goes up with density, so all we have to do is figure out the density ratio increase and multiply the hp.

8psi manifold pressure at 6000ft is: 8 + 11.7= 19.7, then divide by 11.7= 1.68 pressure ratio.

Next is temperature, we'll assume 80° temp going into the intake manifold. We have to use absolute temps, I'm used to kelvin, 80°f is 300°k. 288k (standard temperature) ÷ 300k= .96.

Almost done, multiply the 1.68 pressure ratio by .96 for a 1.61 density ratio increase. Of that 1.68 of boost, only 1.61 of it can be used to increase hp, the rest is heat.

For the final and easy one, multiply the hp by the density ratio. We already calculated your engine is only making 65hp at elevation, so 65 x 1.61= 104hp.

 

Thanks again for that math.

I have amassed quite a bit of information recently but I am still at a standstill.
How do I use my newfound knowledge to find the right turbo?
I can't even find compressor maps to compare.

I think that I could be happy with 104hp. at elevation with 8psi.
Could you recommend a turbo that would do that?

I just don't want to ask "What turbo should I use?" and let you do the work for me,
But... "What turbo would you use?

 

The garrett gbc14 is your best bet.

 

Thanks bbi !

 

I think one thing being missed here is that carburetors act a bit like an intercooler because of the way they deliver fuel. And cool the intake charge. I don't remember the exact number, but i believe up to 12psi, an intercooler isn't even needed. So you won't lose any pressure with an intercooler you may not need.

As for pushing a head gasket, a set of Arp head studs would be worthwhile.

 

Since this is a race only deal you could just cool the fuel before each run if you're using carbs.

 

This is my race bike.
It is the current AMA National Champion in it's class.
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Intercooling hasn't gotten a whole lot of focus since I haven't even gotten a turbo yet.
But, I was kinda thinking that I'd build a custom water to air icebox to chill the air.

Cooling the fuel is an option, keeping it cool is an issue.

Like I said, I'm a total noob when it comes to forced induction and I am greatly interested in any input that you guys may have to set me on the right course.

I want to design a functional kit before I start assembling it.

 

You could build a fuel cooler out of an igloo and a coil of aluminum tubing. Circulate the fuel from the tank through that between runs with an electric fuel pump and a battery.
Nice bike!

 

Turbo and run an methanol. No intercooler or fuel cooler required.