G75-G90 differences?
 

Why should I buy a Supertigre G75 instead of a G90? The G90 has more power in the same dimensions and price is just 7-8 bucks more… the only thing I can think of is the different fuel consumption. Is that an issue?

thanks
david

RE: G75-G90 differences?
 

Go for the 90. You can always throttle back or put a larger prop on it if its a bit over powered. Also you have more scope for future planes. Fuel consumption will be slighly more only if you are using the extra power

Jim

RE: G75-G90 differences?
 

I have a couple of G90's. I second what Jimbo says

Enjoy,

Jim

RE: G75-G90 differences?
 

Jim, Sport Pilot and I each have a Super Tigre .90 with the big S on the side and the bolt on front end. Are these the revving .90s or the luggers, or is that not enough info, I intended to ask you that yesterday and I plum fergitted. Thanks

RE: G75-G90 differences?
 

The G90 with the one piece crankcase with the larger rear bearing and the smaller intake passages is considered to be the lugger. But I still like the 14-6 or 13-8 on the G90's. I've tried the 15-8 and 16-6 on them and they perform like the book says but spool up from idle is slow. They would perhaps, work 'OK' in a scale situation where you were trying to get out beyond the cowl. I get 11,000 with a 14-6 APC and the 108 carb. The 40 carb only gives you about 10,000.

The S90K is the one you are talking about with the two piece crankcase and the squarish head. They look somewhat more massive than the G90.

The S90 is the one with a crankcase a lot like the S90K but it has a round machined head that is sunken in the middle.

The last truely Italion made G90's to come from Italy had a '40' carb on them for some reason. They do a lot better even with the big props when using a ST carb with the flat sidded spray bar or by using a Magnum 108 carb which bolts right in.

They all seem happy with a 14-6. prop

In a diesel situation, the round sided spraybar '40' carb would be better.

Enjoy,

Jim

RE: G75-G90 differences?
 

Not sure what you mean by round sided. My carb appears to be about .60 sized, maybe slightly smaller, has slotted needle on the idle side.

RE: G75-G90 differences?
 

ST has two styles of spray bars, round ones and ones with both sides ground flat to increase the venturi flow area. I have a lot of ST carbs, I use them on other brands that have iffy stock carbs because the ST carbs are infinitely tuneable.

RE: G75-G90 differences?
 

So I should expect about 11K with a 14-6? What fuel, is it limited to low nitro? I have a red head ASP .91 that turns a 14-6 well over 11K but cannot use over 5% nitro. Also weighs a bunch more.

RE: G75-G90 differences?
 

Spraybars

RE: G75-G90 differences?
 

My S75 is a very user freindly engine, a little more so than my g90, the 90 will pull a 14-6 zinger 10,400 and the 75 will only make 10,000. I used both engines in the same airframe and the power differences diminish if you prop the 75 to turn about 1000 more rpm. The 75 with a 12-8 performed about same as the G90 with a 12-10. The 90 WILL cook a piston faster if run too lean for too long.

RE: G75-G90 differences?
 

If a person was looking between these two engines with the intentions of mounting it on a Top Flite warbird, you might want the .75. The .75 will run with the Top Flite in-cowl muffler , but it is too restrictive for the .90, and will cause it to overheat. Other than that, the only reason to buy the .75 over the .90 would be if you got a really great deal on it.

Pilgrim

RE: G75-G90 differences?
 

My brother put a 90 in a 60 size extra...the larger prop would ground-out on takeoff or landings. He wasn't happy, and had to make larger main gear (taller), which made the model look "odd".



Charles

RE: G75-G90 differences?
 

Oh! Having said that above...I just ordered a .75 to put in my .60 size extra... ;-}

Charles