Altitude - Air Density - TPI Intake???
Thread Starter
Burning Brakes
Joined: May 2006
Posts: 1,097
Likes: 2
From: Richfield Utah
Altitude - Air Density - TPI Intake???
Obviously, The higher up in the sky you go, the less air there is. Living here in Utah, we have altitudes as high as 11,000 ft. at the summit. With a nice paved road to get to the other counties in the area...
Now, I live, and spend most of my time at 5500 ft. I am thinking of the logistics on my TPI Corvette intake. So here I am with fuel injection, that has no problems at this altitude. However, Air is a different story. I would logically assume, that larger intake runners, Ported Plenum, and big throated bottom. Would benefit me more than most. The question is, and can I assume, that a 52mm TB would be advantagious? Even though I am not going with heavy mods. Mostly intake, and exhaust. perhaps 1.6 Rollor Rockers, at least on the intake would be advantagious as well. Also, it is claimed that you should increase your initial timing 1/2* per 1000ft. There is even a chart up here at the local college auto mechanics training shop that states the same thing. I power timed my Camaro years ago, on the dyno. It ended up at 23* adv. lead in at crank.
Just thought I would get some of you guru's to give me your oppinions, as this is not something that is brought up very often... Thanks
Now, I live, and spend most of my time at 5500 ft. I am thinking of the logistics on my TPI Corvette intake. So here I am with fuel injection, that has no problems at this altitude. However, Air is a different story. I would logically assume, that larger intake runners, Ported Plenum, and big throated bottom. Would benefit me more than most. The question is, and can I assume, that a 52mm TB would be advantagious? Even though I am not going with heavy mods. Mostly intake, and exhaust. perhaps 1.6 Rollor Rockers, at least on the intake would be advantagious as well. Also, it is claimed that you should increase your initial timing 1/2* per 1000ft. There is even a chart up here at the local college auto mechanics training shop that states the same thing. I power timed my Camaro years ago, on the dyno. It ended up at 23* adv. lead in at crank.
Just thought I would get some of you guru's to give me your oppinions, as this is not something that is brought up very often... Thanks
Burning Brakes
Joined: Nov 2005
Posts: 908
Likes: 1
From: Colorado Springs Colorado
I'm next door in COS, 30% correction factor is not unusual at the place where I Dyno, and it's a good 1000 ft lower that at home. (I live @ 7300 ft. above sea level) Being able to undo that loss with a Roots or Whipple SC has me investigating how to actually shoehorn one in.
Amazing how much differently my car runs at sea level, I'm heading back to Florida for the holidays and can't wait to see how the mods so far run there.
Amazing how much differently my car runs at sea level, I'm heading back to Florida for the holidays and can't wait to see how the mods so far run there.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Not only is the air less dense, but it is under less pressure. Of course that is why it is less dense. A greater air flow capacity won't make for greater air flow, until you max out the capacity you have. At altitude you could do just as well with smaller air passages. What you need is more pressure. Try either a dose of sea level air or a blower. The last time I had my car at sea level, it ran a full second quicker in the 1/4.
The lower octane gasoline is a reflection of the lower combustion pressures possible with the less dense air. I have experimented with my car at the race track, and I have my base timing set at 14° BTDC. It seems to run the quickest and it doesn't ping or knock. You might experiment and see what works best for you.
RACE ON!!!
The lower octane gasoline is a reflection of the lower combustion pressures possible with the less dense air. I have experimented with my car at the race track, and I have my base timing set at 14° BTDC. It seems to run the quickest and it doesn't ping or knock. You might experiment and see what works best for you.
RACE ON!!!
Thread Starter
Burning Brakes
Joined: May 2006
Posts: 1,097
Likes: 2
From: Richfield Utah
I have to agree. Forced induction would be the ticket, but not on my budget. 1 second quicker at sea level is a huge amount. That just goes to tell you a little bit about altitude. Living in the Salt Lake area. You may be a little lower than I am, but it ends up being about the same. All you have to do, is drive a few miles up Parleys canyon, and the cottonwoods. Your up there with the best of em 
I've got to get the air out once it's in, and I have all the stock exhaust that come with my 88 main cats, pre-cats, and stock headers. Interesting, I guess everybody else in this area are sucking the same air. So that evens the competition up a little... 
I've got to get the air out once it's in, and I have all the stock exhaust that come with my 88 main cats, pre-cats, and stock headers. Interesting, I guess everybody else in this area are sucking the same air. So that evens the competition up a little...
Le Mans Master
Joined: Feb 2002
Posts: 7,858
Likes: 2
Back when I was flying, Density Altitude was a big factor in aircraft performance, of the low perf single engine piston Cessnas and Pipers I flew. On a day with a higher density altitude, the 4 seat Piper Cherokee became a two seater.
There was a form of forced induction that always intrigued me, with some piston singles, I think some of the Lycomings in the Beech Bonanza models had an STC (Supplemental Type Certificate) for turbo normalizing. It was a turbo but all it did was normalize the induction to sea level performance, regardless of altitude. The advantage, as I understood it, was that the lower boost didn't lower the TBO (Time Before Overhaul) on the engine, but you could be at say, 15,000' and the the engine would perform as though you were flying at or near sea level. I can't remember much about it though, might be mistaken about the boost, it might have been significant boost to duplicate sea level pressure @ 15,000 for instance.
There was a form of forced induction that always intrigued me, with some piston singles, I think some of the Lycomings in the Beech Bonanza models had an STC (Supplemental Type Certificate) for turbo normalizing. It was a turbo but all it did was normalize the induction to sea level performance, regardless of altitude. The advantage, as I understood it, was that the lower boost didn't lower the TBO (Time Before Overhaul) on the engine, but you could be at say, 15,000' and the the engine would perform as though you were flying at or near sea level. I can't remember much about it though, might be mistaken about the boost, it might have been significant boost to duplicate sea level pressure @ 15,000 for instance.
Melting Slicks
Joined: May 2001
Posts: 3,014
Likes: 18
From: Raleigh, NC
Just put a 100 HP nitrous shot on it. That should duplicate the HP gain of sea level.
I moved from Layton, UT, down here to NC about 2 years ago. My car picked up .7 and 5 MPH the first time I went down the track. Utah sucks man.
I moved from Layton, UT, down here to NC about 2 years ago. My car picked up .7 and 5 MPH the first time I went down the track. Utah sucks man.
Thread Starter
Burning Brakes
Joined: May 2006
Posts: 1,097
Likes: 2
From: Richfield Utah
Originally Posted by neat
Just put a 100 HP nitrous shot on it. That should duplicate the HP gain of sea level.
I moved from Layton, UT, down here to NC about 2 years ago. My car picked up .7 and 5 MPH the first time I went down the track. Utah sucks man.
I moved from Layton, UT, down here to NC about 2 years ago. My car picked up .7 and 5 MPH the first time I went down the track. Utah sucks man.
The State does have a few good qualitys, I guess...
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