What turbo system to get???

[knightrida13]

Hey... I am considering buying a 240sx. I want to experience the rear wheel drive world. However I know nothing about Nissan 240sx's. If I get one I would like to be able to run high 13's (13.6-13.8) I would like to keep in the stock engine because I have heard that it has a high torque curve and with a turbo the car would hall ***!. Is this true? If it is possible I would like to know what turbo to get and where I can buy it for not to much and gfet it installed. (I live in southern california) I will be moving to camp pendelton in a few weeks becasue I'm a marine so anything in the L.A. and san Diego area would be ok. i really need information and cost possibilities soon becasue if I don't get a 240 then I'm just gonna get a 99 mitsubishi eclipse gst becasue its already turobcharged and I could just get a upgrade for not to much and be abel to run some good numbers. Any info you can give me is greatly appreciated. Thanks

[matt0941]

You do not have to even replace any stock internals on the KA as long as you go with a turbo that is not huge and keep your PSI at or below 10. And yes it is a torquey (sp?) motor and your questions have been asked alot before (13.6 is very doable) just do a search in the TURBO KA forums with the word turbo, you get about 200+ results alot containing good information.

[C-Kwik]

Actually bigger turbos will generally result in more power at the same boost level. Especially bigger turbines. There can be too big of course, if you get a turbine so big that it can never reach max boost, but we will try to stay reasonable. Larger turbines produce less backpressure since the flow more air. Larger compressors tend to be more efficient as well, especially as you get to higher boost levels. And then there is the shift in where power is made.

As a reference, check out this dyno chart:

http://www.xs-engineering.com/...t.htm

Never mind the star at 217 lb-ft of torque. Let's look at the peak HP. It makes about 227 HP at 5500 RPM. If you convert that to Torque, it's making about 217 lb-ft of torque at 5500 RPM. Lets say we put in a larger turbo and it made the same amount of torque, but now at a higher RPM. Lets just assume 6000 RPM. 217 lb-ft of torque at 6000 RPM is 247 HP. This is quite indicative of what can occur in upgrading to larger turbos.

A great example of a car I saw this occur on was my friend's Supra. I wish I had the dyno chart to show you. But the Stock Supra has a relatively flat torque curve. I believe the peak Torque is 315 lb-ft. We swapped out the stock turbos for a rather moderately sized T04R. We limited boost to only 14 psi. The torque curve was amazingly linear, but increased with RPM. Actually, it followed the HP curve so closely, it was hard to distinguish the two. After about 5000 RPM, the torque levels out and even starts to drop off towards redline. But HP continues to go up. The Torque peaked out in the upper 300 range. IIRC the stock boost is about 12 psi. Considering only a 2 psi increase, the max HP went up to 450 at the wheels. At the crank, you're probably looking at about 500 HP. I will say though that the stock turbo system is restrictive overall. All the piping for the sequential set-up sits in a heave block of twisted metal in a space about 2 cubic feet. I'd venture to guess an easy 50 HP could be pulled out from removing all the sequential valving and producing a freer flowing manifold alone. But either way, an estimated increase of 180 HP at the crank from only two psi of boost more and a larger turbo is something to think about. And people wonder why I'm a fan of bigger turbos.

[matt0941]

Actually, it followed the HP curve so closely, it was hard to distinguish the two. After about 5000 RPM, the torque levels out and even starts to drop off towards redline. But HP continues to go up.

I don't know if you are trying to say that this is odd in any sense, or just pointing it out, but it is not odd just to clarify. Horsepower always continues to rise with RPM, while torque has a certain peak, and will then decline from that given point.

[C-Kwik]

I don't know if you are trying to say that this is odd in any sense, or just pointing it out, but it is not odd just to clarify. Horsepower always continues to rise with RPM, while torque has a certain peak, and will then decline from that given point.

Most torque curves have usually rise early, and then level out. HP curves are generally much more linear than the torque curve(rises with RPM). But in this case, they were nearly identical until the torque started to flatten out somewhere in the neighborhood of 5000 RPM. I'm not saying it is odd, it's actually quite typical of larger turbos. But factory motors tend to have a flatter torque curve for better drivability.