XS 550 Opinions

[thedude]

In the CTS-V world pulley swaps are common. With smaller diameter pulleys you can get about 12-14 lbs of boost near sea level safely with the stock supercharger (stock boost is about 8 psi). It would be interesting to see if you could work with Nautique/PCM to develop a pulley combo for high altitude operation. Of course it would require an ECM re-tune by PCM.

OR

Just get a more aggressive prop.

[Zach@n3]

Yeah, I doubt stock tune would be able to compensate even with the 02's and map sensor. Would be cool to try seeings how these things are monsters!

[jsta281]

no way PCM approves any pulley swap

[jsta281]

I was not finished

And retune if they won't ok octane additive. However, if you were not concerned about the voiding your warranty a pulley swap tune is very straightforward For somebody who has HP tuners Or some equivalent.

[perry386]

A couple of things: First, I have no specific data or experience with marine applications. However, I am very familiar with positive displacement type super chargers, and somewhat familiar with the the Cadillac version of this motor. Here are a couple of comments on what has previously been posted. 1) a super charged engine not being as effected by altitude is not correct. It is not correct because the density of the air coming in still decreases the over all cylinder pressure as compared to what it would be at a lower elevation. The exception to this rule would be a supercharger with a blow off valve or similarly a turbo charger with a BOV, that is because the amount of air being pressurized and introduced into the intake can be manipulated or you can "turn up the boost" to compensate for the elevation. A belt driven PD motor has no BOV so it will still make less power at altitude. 2) Engines at altitude require less octane because the cylinder pressure will be less. That is not a suggestion/recommendation to run less octane, but if 91 is required at sea level it is almost a certainty that 89 octane would be sufficient at 5500 ft. However, if octane is a concern there are excellent products for boosting octane and increasing knock prevention. Torco makes a product Torco Unleaded Accelerator that works. I have been running it in my PD blower mustang for 8 years. I have standard CATS and O2 sensors. I run 21 pounds of boost (making 656 hp out of my 281 cid) on my stock motor adding 32 oz of Torco to ten gallons of 91 fuel that makes my octane approx 97. 32 oz of this product into a tank of fuel would easily "cure" any issue with mid grade gas being run in a stock application. It certainly would be alot eaiser to hall around then tanks of premium fuel.

As for longevity obviously that is a unknown as far as empirical data with the engine being new. That said PD blowers have been around, even in factory or standard equipment applications, for a long time. My 91 Thunderbird super coupe had one and It had 180K on the clock when I sold it with no super charger issues. I am not as well versed in the GM platform motors as I am with the Ford, but routinely rubbing shoulders with GM guys with that run these LSA positive displacement motors leaves me with little concern regarding longevity. A PD motor on "low boost" (10 lbs or less) would not have me concerned whatsoever in terms of being hard on the long block, the only concern would be if being under load most of the time (read boost here) as compared to a car (which is rarely under boost unless under heavy load or acceleration) would cause the PD blower to require more frequent maintenance/rebuild as compared to a car. My guess would be it would not.

So if my ZR6 390 has nock to it then this octane booster stuff will get rid of that?.....I live in Alabama so elevation is of no concern

[jsta281]

So if my ZR6 390 has nock to it then this octane booster stuff will get rid of that?.....I live in Alabama so elevation is of no concern

Well that depends on what is knocking, but if you are getting detonation as a result of low octane fuel then yes. However if you are running a stock tune at sea level on 93 octane fuel and have detonation then I would think something else is going on. However if you are not running 93 octane fuel (as in it is not available) then I would definitely try it. By the way the info I provided previously on mixing ratio came from posts authored by James Parker from mobile Al. He is a well known tuner of Ford and GM late model cars. He is who in fact tuned my Mustang. I'm not sure what the status of his shop in Mobile is but he is in my opinion one of the best tuners in the country and he endorses Torco as a fuel additive.

[gride]

i'm from mobile. do you know what the name of his shop is or was? i'm always looking for a proper mechanic.

[jsta281]

i'm from mobile. do you know what the name of his shop is or was? i'm always looking for a proper mechanic.

RWTD Runnin With the Devil

To be completely straight I'm not sure what the status of his shop is, I hear he spends some time in Colorado tuning as well it seems, and this is just speculation, he got burned out a bit and does a lot less and I'm not sure he even has a full time shop anymore. But He is as good as anyone in the country when it comes to custom tuning.

[perry386]

Well that depends on what is knocking, but if you are getting detonation as a result of low octane fuel then yes. However if you are running a stock tune at sea level on 93 octane fuel and have detonation then I would think something else is going on. However if you are not running 93 octane fuel (as in it is not available) then I would definitely try it. By the way the info I provided previously on mixing ratio came from posts authored by James Parker from mobile Al. He is a well known tuner of Ford and GM late model cars. He is who in fact tuned my Mustang. I'm not sure what the status of his shop in Mobile is but he is in my opinion one of the best tuners in the country and he endorses Torco as a fuel additive.

We are running regular 89 unleaded...the cheapest we can find haha

[gride]

I'll ask around. I know a few older mechanics that have been in this area longer than I've been alive. Does he know marine stuff at all? And the only tuning I may need is on a 71 jag. Is that in his area at all? I don't want to waste my time or his time. Thanks.
-I just found the shop address , but the mailing address is Colorado so ill find out tomorrow one way or another.

[jsta281]

We are running regular 89 unleaded...the cheapest we can find haha

It would be cheaper to buy 93 then buying 89 and adding Torco.

[jsta281]

We are running regular 89 unleaded...the cheapest we can find haha

Buying 93 would probably be cheaper (and certainly less hassle) then buying and adding Torco.

[jsta281]

I'll ask around. I know a few older mechanics that have been in this area longer than I've been alive. Does he know marine stuff at all? And the only tuning I may need is on a 71 jag. Is that in his area at all? I don't want to waste my time or his time. Thanks.
-I just found the shop address , but the mailing address is Colorado so ill find out tomorrow one way or another.

I doubt he does any marine stuff and all I know is he well know for tuning cars with a modern pcm

[perry386]

It would be cheaper to buy 93 then buying 89 and adding Torco.

Would 91 fix the knock? Because it is a whole lot cheaper than 93 down here.

[jsta281]

My guess would be yes. I'm sure running anything lower at your altitude would ping and knock.