[JamesNoBrakes]

Originally Posted by 95 imp

The purpose of a waste gate is to automatically limit boost pressure.

https://en.wikipedia.org/wiki/Wastegate

Sure, but ECUs/actuators and mechanical devices on cars are not programmed to provide zero turbo boost at SL and slowly build it up to full at altitude like an airplane.

Perhaps, all the lag is caused by improperly sized turbos/systems....

https://www.hotrod.com/articles/what...g%20situation.

In general, yes, that is part of it. Bolt on turbo kits are generally not optimized for the engine and system. Modern turbo tech uses things like twin scrolls positioned right next to the exhaust valves/manifold where there's very little loss, or hot-V setups or some other setup. Smaller turbos respond faster, etc. Modern turbo engines can develop full torque and keep it flat to peak from around 1500rpm. That's why engines like the BMW 6 and 8 cyl are such killers in terms of acceleration/power, they have a huge amount of torque under the curve and it's available from a very low RPM. Other modern setups are doing things like electric-powered turbos or hybrid drives that take over for the low RPM range where the turbo doesn't have enough pressure. The only real "lag" in these systems is from throttle programming and being in the wrong gear (transmission having to shift several times). These are ways that we are increasing efficiency and power at the same time, without a big hit on drivability, etc. But this is really not related to bolting a turbo on to your car, as you won't be able to replicate this with a turbo kit.

A factory air intake is limited by several factors. The EPA has noise restrictions, the factory has restrictive filters for longevity reasons, packaging issues, etc.. Although, I will admit the factory is getting way better at optimization of their motors reducing the need/gains of a CAI.

https://en.wikipedia.org/wiki/Noise_...c_right-of-way
"This provision is an objective emission control. It applies maximum sound levels to various categories of moving vehicles and for several vehicle speeds. It is the backbone of vehicle sound emission regulations. It generally requires a measurement of A-weighted sound level of a moving vehicle at a specific distance from the vehicle path (normally 50 feet)."

The reference to "cold air" is air from the exterior of the heated air in the engine compartment. Back in the day, most/all manufacturers took "under hood air" hence "cold air intake". Again, the manufacturers have been optimizing their designs (within applicable regulations/design goals) to improve power numbers.


As far as dyno tests of CAI's, name two dyno's that measure ANY performance upgrade accurately. They are all over the board, relatively speaking, even from the same manufacturer.

It's well know how CAI's are "snake oil". I've had them on cars. Nothing big against them, having that additional sound can be a nice addition and some people like how they look in the engine bay. I would not recommend this to someone trying to make up for altitude. It's just pissing away money (for that purpose).

[95 imp]

Originally Posted by JamesNoBrakes

Sure, but ECUs/actuators and mechanical devices on cars are not programmed to provide zero turbo boost at SL and slowly build it up to full at altitude like an airplane.

When you can drive a car from SL to 10k feet and back in a minute or 2 I'll worry about that. But, if you REALLY wanted to, you could get a baro-actuated electronic waste gate to solve that problem. Which is totally ludicrous because it's a car. I'm not trying to shoot down a Zero. I'm cruising and the altitude change is per hour (generally).

Originally Posted by JamesNoBrakes

In general, yes, that is part of it. Bolt on turbo kits are generally not optimized for the engine and system. Modern turbo tech uses things like twin scrolls positioned right next to the exhaust valves/manifold where there's very little loss, or hot-V setups or some other setup. Smaller turbos respond faster, etc. Modern turbo engines can develop full torque and keep it flat to peak from around 1500rpm. That's why engines like the BMW 6 and 8 cyl are such killers in terms of acceleration/power, they have a huge amount of torque under the curve and it's available from a very low RPM. Other modern setups are doing things like electric-powered turbos or hybrid drives that take over for the low RPM range where the turbo doesn't have enough pressure. The only real "lag" in these systems is from throttle programming and being in the wrong gear (transmission having to shift several times). These are ways that we are increasing efficiency and power at the same time, without a big hit on drivability, etc. But this is really not related to bolting a turbo on to your car, as you won't be able to replicate this with a turbo kit.

Then I guess you buy parts and design a system for your engine. And, if properly designed, you CAN replicate that performance. Kinda like we do with headers, exhaust and cams.

Originally Posted by JamesNoBrakes

It's well know how CAI's are "snake oil". I've had them on cars. Nothing big against them, having that additional sound can be a nice addition and some people like how they look in the engine bay. I would not recommend this to someone trying to make up for altitude. It's just pissing away money (for that purpose).

Thanks for your opinion. You may very well be correct with modern engine design, especially being used on otherwise stock motor.

[Idaho2018GTPremium]

I am of the opinion that an aftermarket "CAI" doesn't add any power. The product dynos are done w/ hoods up which means the filters are free to suck in air from anywhere inflating the numbers compared to the hood down, rather than sucking air from just the smaller opening from the front grille when the hood is down, and the manufacturers most likely compare a heat soaked factory CAI run to a cool aftermarket CAI run to show their supposed "gains".

If you want to get more power, there's tried and true ways: Cam, headers, ported intake manifold, ported heads, E85/ flex fuel tune, etc. Or, forced induction (supercharger). You'll make more power at elevation, but you'll also make even more power at sea level.

Remember that elevation is only part of the story: Density altitude factors in air temperature, barometric pressure, humidity, among other things and all affect how much power an engine makes. A low DA makes more power than a high DA all else equal. A 32 F cold day at 2000 feet elevation will have a lower density altitude than a 100 F day at 100 feet above sea level - which means an engine will make more power at those more favorable conditions (very cold air + moderate elevation). Hot air will have a higher DA than cool air at the same elevation. Very cold air brings the DA down lower. For a stock 455 hp car, you're talking probably a 60-80 hp swing between a 100 deg F day and 30 deg day, depending on other conditions.

Also, SAE ratings are done under certain conditions, which assumes 77 deg F air and 29.31 inches mercury barometric pressure. That equates to a density altitude of around 2,100 feet. SO, if it is cooler than 77, and the barometric pressure is higher than 29.31, the LT1 engine will make more than 455 hp. If the air temp. is warmer, and the pressure is lower, the engine will make less than 455 hp.

[vtirocz]

Originally Posted by JamesNoBrakes

There isn't any good way I've ever heard of to "keep SL power" on a turbo-car.

Maintaining the sea level torque curve up to certain altitude levels is definitely possible and is the industry standard with modern turbocharged engines (obviously controls strategy and hardware dependent). It's unlikely to maintained > 4k feet though (or ambient pressure / temp combinations less favorable than that), but will lose much less power than a naturally aspirated engine if set up right.

[JamesNoBrakes]

Originally Posted by vtirocz

Maintaining the sea level torque curve up to certain altitude levels is definitely possible and is the industry standard with modern turbocharged engines (obviously controls strategy and hardware dependent). It's unlikely to maintained > 4k feet though (or ambient pressure / temp combinations less favorable than that), but will lose much less power than a naturally aspirated engine if set up right.

I would need proof for this. So you are claiming that a turbo car is set up to maintain torque as air pressure decreases? First I've ever heard of this.