New Turbo to big a pressure drop ??????????

[paulmc]

See pic, VR4 mainfold Nissan T25 turbo.

I am not sure if the pressure drop will make it very laggy.

As the gasses flow from the maniflod to the turbo there will be a velocity, pressure and temp drop which may slow the turbo. I THINK

I have always thought of pressure temp and velocity in simple terms.

If you whistle put your hand in front of your mouth and the air is cold, i.e high pressure in your mouth coming out to open air so temp and pressure drop.

If you cough and put your hand over your mouth it will be hot air, well the same temp, pressure and velocity as the air in your lungs

SO, will this cause to big a drop acorss the mainfold to turbo. I am stuck.

any engineer types out there /help /help

Thanks to Zedy1 for maniflods, good deal.

cheers

Paul

[psbarham]

i take it you mean if you make up an adaptor plate to convert from 3-4 studs and the resulting extra length . well my advice is take it to your local engineering co. and see what they can do out of 1/2 - 3-4" plate and then fix the plate to either the manifold or turbo with countersunk screws (&copper grease) therefore less length if you do have to make a pipe up try insulating it with that exhaust bandage from demon tweeks it used to work quite well on tuned cossie's . it keeps the exhaust gasses hotter and therefore higher velocity. hope this makes sense to you ,got a migrane off too bed now

[psbarham]

oh damn it you've got me pondering now and i just had a look at the pic's again and all that springs to mind is 'sqaure peg round hole' looks like you need a new manifold making , a nice tubular stainless one cooooool, but pricey but if your going that route you then have the choice of just about any turbo you want , right definatly off to bed now

[Nick Mann]

The size of the pipes matter for volume only. How much volume is there inside the Nissan turbo before the air hits the turbine, and how does it compare to the VR4?

I am no expert, but I would imagine the turbine size and weight of the moving parts of the turbo would make much more difference than a small change in volume between the cylinders and turbo.

What kind of gas flow did the turbo see on the Nissan?

[paulmc]

I would need to find the compressor map, they are making around 250ish @ 18psi on the Nissan.

I don't mind more lag because the turbo is physically larger, I was just a bit worried about the rapid change in pipe diameter slowing the flow down. This may not even be a consideration I just aint sure :embarasse

[Nick Mann]

Increase in diameter will slow down air speed. The flow will be constant. The point is, how much volume of air was the turbo designed for? If the engine was a 2.0l or bigger with one turbo, will it be appropriate to put it on effectively a 1.25l engine? The speed of gas flow will have been a consideration when the turbine was designed, but are you going to put a similar amount of gas through it?

[paulmc]

There will be more than enough flow, The Nissan S13 is only an 1800cc. with the 2 turbos there will be enough flow for around 430 prob 480 at a push.

As for the amount of gas going through it, the T25 is a pertty small turbo really 2 of them will be more laggy that the origional set up but I expect that. On the flip side I should have a lot more flow higher up the rev range.

[ako]

Sliiightly confused here by what you're worried about..

If you mean you're worried that the manifold runners could possibly be a bit long - its nothing at all to worry about, even with an adaptor plate they are still DAMN short length runners regardless.

Like you said yourself - of course its going to be slightly more laggy. On the other hand, its nothing you won't be able to adjust to in no time at all.

Maybe try twin T51R's on the thing.. That might pose some driveablility issues on the other hand :evil2: