front mount versus rear mount?

[jtssrx]

I stand corrected. From the research I did today the Simons uses a GT25. That is identical to teh stage 2 bender that makes 220 hp.

 

[Simons CPR]

jtssrx, i also did some research for you, Here is some stats on the differences between the Simons CPR RX-1 intercooler and the Bender Racing RX-1 intercooler. i believe the size differences are the same between vector and rx-1 models as well. the CPR dimensions are 8 x 14 which is 112 in. of surface area and has 17 transfer tubes, on the other hand Bender's is 5.5 x 9.75 which is 53.62 in. of surface area and has 15 transfer tubes (but the end one on the right is pretty restrictive, so it probably flows more like 14.5 tubes) Thats over twice the cooling surface area with two more transfer tubes availible to my intercooler, so which intercooler do you think works better than the other? And which one needs a tunnel cooler to try to equal the playing field? how effective is the rear cooler? it runs right next to the 1400 degree exhaust pipe, so maybe not as effective as you would think. jeff

 

[Simons CPR]

our apex turbo uses the same size intercooler. jeff

 

[woodsrider]

jeff - what's the delta-t of the air that flows across your intercooler vs. the air that flows across the bender intercooler? With the front mt turbo I'd think there would be alot more heat under the hood thereby requiring a much larger intercooler to achieve the same cooliing as a rear mt turbo.

 

[snowy1]

thats the point I have been tryng to make the cooling area of the front mount makes it cool as will as a rear mount there four no hp. gain for the rear mount over the front mount especially if the front mount is running with out a hood or with a very well ventilated hood.

 

[Simons CPR]

on the front mount turbos, the intercooler and compressor side of the turbo see alot of cold inlet air. the turbine side is in a heat shield that contains most of the heat. the gt25 has a liquid cooled bearing housing to limit heat transfer between the two housings and extend turbo life, we use this water cooling feature, which greatly reduces heat transfer between the two housings, giving you the lowest discharge air temp possible. the rear mounts do not use this feature which allows alot more of the turbine heat to transfer to the compressor side, leaving the rear mounts with inherently higher discharge air temps due to more heat transfer from the turbine side of the turbo. jeff

 

[TurboKeith]

The pic with the two intercoolers next to each other really puts it in perspective. You have way more surface area on yours. Have you ever measured your intake air temp at the carbs?

 

[ken_climb]

thats the point I have been tryng to make the cooling area of the front mount makes it cool as will as a rear mount there four no hp. gain for the rear mount over the front mount especially if the front mount is running with out a hood or with a very well ventilated hood.

I could take my hood off to! :ORC

 

[jtssrx]

Before you guys take this as pure fact give me a day or two. I'm getting the technical data On the inter-coolers as we speak. Just because it's bigger doesn't mean it's better. If that was the case everyone would oversize there inter-cooler. There is a calculation that tells you the size your suppose to use. The inter-cooler Bender uses was sized by a turbo/inter-cooler manufacture. I'm in the process of finding out what numbers factor in on Inter-cooler sizing. It's alos very close to the same size as the MC express and they have been building turbo kits for multiple years.

As far as the premise that your reducing heat between the housing with coolant and that gives you a discharge Temp advantage Your purely speculating Jeff. Unless you've had a rear mount and pulled the numbers you can't say that's true. You also can't say, well I've simply shut off the water on my kit and I saw a 20 degree difference. Your Turbo is in a very confined area. Your Turbo may be sitting in a more heat restricted environment and the water helps your turbo. The bender is not boxed in like your turbo. It has a large ventilated area to breath. So it might not need the water like your turbo does.

One more thing I was told by turbonetics that the water cooling feture is there to extend the life of the bearing only. not to reduce temps between the housings.


My Lightning Pro had a very low Compressor side temp. In most cases I could touch it. The turbine side was another story and that's why I had a heat blanket on it. As you can see in the pictures.

 

[jtssrx]

OK Just got off the phone boys. here's the deal. Most air-to-air inter-coolers are only 50-65% efficient. That means for example, that with 11psi boost and its 120°f air charge temperature increase, an inter-cooler reduces the air charge temperature only 60 degrees. Also, an inter-cooler will reduce boost 2 - 4 psi. on average.

So with the increases size of you the inter-cooler on the simons you have to increase the boost pressure to get the same amount of pressure the Bender has. Example if you want 8 pounds of boost pressure the bender is actually making lets say 10 to get 8 on the other side of the carbs. With the increased size of the CPR you should have to make more the 10 pounds of boost to get the same 8 pounds of pressure at the other side of the carbs. By doing that your actually increasing the heat made when the air is compressed so you rendering the extra size of the inter-cooler useless.

I to would have to have both kits to prove this as fact but that's a general rule of thumb. So another words you get to a point where making your inter-cooler larger is useless.

 

[Turbo Tim]

OK Just got off the phone boys. here's the deal. Most air-to-air inter-coolers are only 50-65% efficient. That means for example, that with 11psi boost and its 120°f air charge temperature increase, an inter-cooler reduces the air charge temperature only 60 degrees. Also, an inter-cooler will reduce boost 2 - 4 psi. on average.

So with the increases size of you the inter-cooler on the simons you have to increase the boost pressure to get the same amount of pressure the Bender has. Example if you want 8 pounds of boost pressure the bender is actually making lets say 10 to get 8 on the other side of the carbs. With the increased size of the CPR you should have to make more the 10 pounds of boost to get the same 8 pounds of pressure at the other side of the carbs. By doing that your actually increasing the heat made when the air is compressed so you rendering the extra size of the inter-cooler useless.
I to would have to have both kits to prove this as fact but that's a general rule of thumb. So another words you get to a point where making your inter-cooler larger is useless.

You're making it sound like the cpr turbo works harder to achieve 8 p.s.i of boost ,because of a larger intercooler . However , my experience is that the bender unit works harder to achieve 8 p.s.i. of boost because of all the tubing related to getting the air from the rear of the sled to the front . I've tinkered with both kits this past winter and it was much easier to overboost with the frt. mount than with the rear mount. ( Both have the same turbo unit ). My .02

 

[jtssrx]

Turbo Tim: If X area is larger in volume to Y area and your trying to maintain equal pressure in those areas you have to increase the rate at which your filling the area to achieve equivalent pressure.


The only way to true prove any of this is to take both turbo systems and measure pressure's and temps.


But the theory's prove out. You can't argue with the math.


I'll say this again to. If I had 5K and I had the choice I'd pick the front mount.

 

[Turbo Tim]

Turbo Tim: If X area is larger in volume to Y area and your trying to maintain equal pressure in those areas you have to increase the rate at which your filling the area to achieve equivalent pressure.


The only way to true prove any of this is to take both turbo systems and measure pressure's and temps.


But the theory's prove out. You can't argue with the math.


I'll say this again to. If I had 5K and I had the choice I'd pick the front mount.

My point exactly ..........when you include the charge tubes , the Bender unit has much more volume to be filled than the CPR unit .

 

[snowy1]

if you look at them the plenum is much larger on the bender and then the longer charge tube looks like there is as much if not more volume for the compresser to fill on the bender just less inner cooler.

 

[woodsrider]

I'm going to weigh in one last time. Each mount has its own pros and cons. Each rider has his own riding style and riding enviroment. If all you do is ride trails and drag race then the front mount is the only way to go. If you boondock and frequently ride in deep powder snow then the the front mount is not an advantage over a rear mount because you don't hook up like you do on hard pack and you get a lot more track spin without much forward momentum(thereby turbo lag is not a factor). All tubos/super-chg are great. One could never go back to a naturally aspirated machine again (as far as I'm cocerned). Even though the turbo's are much heavier than the super mod 2-strokes, the light weight 2strokes just can't hold a candle to the turbo power or even come close to the dependability and longevity of the 4strokes.
If everybody liked the same thing, then we would all be chasing the same woman.