yes: The air pressure is lower so there is less oxygen, lower effective compression, etc. The ECM compensates be reducing the fuel accordingly.KipS said:Is the reason for the the performance loss because of the lower oxygen level. And do cars with turbo's experience the same drop in power?
You are right about the STIs. They are a big part of the reason I am modding my Z06. I just can't stomach having my doors blown off by a Subaru. My '94 S4 Audi has all of the Euro RS2 "go fast" mods including a bigger turbo and boost up to 24 psi. It pretty much rules on Vail Pass and the tunnel approaches.novetteyet said:I agree with RalphP - turbo cars typically do not lose as much up here. So be careful with those STIs. AWD + not losing much power like we do, and they can eat you for lunch. Get used to having a mid 13 second car!
You will *really* notice the altitude if you drive up to higher elevations from Denver. At 10,000 ft, the car feels like a *#(&@ Civic.
Chris: Thanks for all the information. The only other thing to remember is that a turbocarged vehicle is primarily designed for sea level performance. To compensate for altitude, it has to take in a greater volume of air, compress it and provide the sea level equivalent volume and pressure at the inake manifold. The only way to do it is to spin the turbo faster. Most factory cars use the smallest turbos possible since larger turbos take longer to spin up and induce unwanted turbo lag. Hence, there is a limit to how fast the small turbo can spin and to how much air it can compress and deliver though the intake system. That limit will dictate a maximum altitude at which the car can maintain its' sea level performance. Above that altitude, the car will perform worse than sea level, but still better than its' normally aspirated cousins. BTW: compressing all that air heats it too, and most of the factory intercoolers can't keep up on hot days in Colorado (the air to air intercooler loses heat transfer efficiency at altitude) so pick a hot day to mess with an STI.Chris310P said:Turbos and superchargers depending on boost can make up for the pressure loss at higher altitudes and basically makes the car or aircraft act like it is at sea level pressure.
I know whatcha mean. I've long wished Chevy offered a version of the Vette with a mid sized TT V8. Maybe 4.8L TT or thereabouts. Forced induction seems to rule at high altitudes.RalphP said:You are right about the STIs. They are a big part of the reason I am modding my Z06. I just can't stomach having my doors blown off by a Subaru.
Cool. Be curious to know how you like the H/C. I had a SC on an old 96 Z28 I used to have, and I was never happy with it. The car seemed to run rough, like a strange wobbling sensation, at low RPMs and I think it was due to the lateral force on the engine shaft from the SC belt. If I left everything alone but removed the belt, it ran smooth as silk at any RPM. Also the SC blew my head gasket, and added weight to the front end of the car.I'll see how I like the H/C on the Z. For various reasons, I decided not to go with a SC. If I need more, then the next step may be a 427.
Kip: Frankly, a supercharger is probably the most bang for the buck, albeit a big buck. However, originally, I did not want to spend that much or deal with various complications.KipS said:That's all great info. Thanks. Do you have any recommendations other than a supercharger that are easy to do to regain some of the losses.
Tony: I agree with you on all points. Also, I don't mean to imply that I street race because I really don't (kinda sorta mostly). For me, it is usually enough to be able to smile and know I can kick butt. But, the real question here is how to get the cars to run the way they do at sea level. I forgot Nitrous as probably the most economical solution - so thanks for adding that! Is it practical for occasional street use?TonyJ said:So far, I haven't been convinced that headers are good bang for the buck on these cars. They are just too damn expensive. 30-35 hp for $2K is weak. The cheapest solution is almost $1500... That said, it's probably my next mod.
I'm actually very pleased with the Z's performance, stock. I'm adding a 100 shot of N02 for those times I want to blast it down the track. I went crazy with the safety stuff on the nitrous and am still under $1K. That's bang for the buck! 450 at the wheels, but only when I want it. I can also pull the setup and sell it if I change my mind.
Some folks like to have the power under tap at all times, but I'm not really a street racing fan. That's not to say I've never done it, but it's really pretty irresponsible... Although, I have to admit probably drive the 'vette faster than the f-body, on a daily basis. The 'vette handles so well, it feels really safe.
The supercharger is probably one of the best mods for these cars, but it just feels contrary to their original design. These are high compression, high-reving, n/a motors. Perfect for nitrous, not so perfect for s/c... Now, if you're going to do a rebuild, my thinking flips. Forge the bottom end, lower compression and add some serious boost. Now you're back into some serious buck bang.
The work is being done at Dragonrace Engineering. I will be able to recommend them, I hope, after the completion of this work as it is really the first work they have done on my car. I visited at least 1/2 dozen Vette shops in Denver. I chose Dragon, most simply, because he has his own dyno and nobody else does! He also has a flow bench. If you are serious, you have to get the tools, right? Anyway, if you are seriously thinking of having work done in Denver, PM me and I will be happy to pass on what I learned. :z:novetteyet said:Ralph -- Do you get your work done in Denver? If so, where, and would you recommend them?