Topic: turbo crawler build

[lilbluej]

i need to start this build with a couple of questions and if you guys could answer them that would be great. the plan is to let this thread die and i will drag it back up after i begin the build.


1. do i need a blow off valve? is it there for any reason other than keeping the turbine spinning as fast as possible?

2. is there a noticeable performance loss with having the turbo mounted on the passenger side of the engine compartment?

i've heard that the closer to the exhaust the better. my goal is to get a quick spooling setup and i don't want any extra lag from having the turbo mounted in the wrong spot. on the other hand having it on the passenger side would require a lot less fab work. 

i need to build power quick for crap like this: http://www.youtube.com/watch?v=VC09e6jHhJ4

thanks
Matt.

[lilbluej]

specs are

2.5 from a 98tj with 4.0 throttle body, exhaust w/ muffler but no cat
A904 (30RH)
np231 w/ 4to1 kit
5.40's in the diffs
rolling on 37inch BFG stickies but would like to step up to 39's

[dwtaylorpdx]

Blow off valve/Bypass valve = Yes, It makes the most difference at lower RPM.

Properly plumbed you should not notice the difference between either side if you size the piping correctly.
You will get better performance if you pair the exhaust pipes based on firing order  (1,4) (3,2) with a Y pipe into 2 tubes,
and keep them separate to the turbo flange. This helps with off the line torque and spool up, but limits the top end at higher RPM's a bit.

At least thats my experience on turbo setups in general.

Dave

[lilbluej]

thanks dave.

[lilbluej]

what size pipe would be best for routing under the oil pan to the passenger side mounted turbo?
i plan on using the stock manifold and wrapping the pipe in header wrap.

for fuel i'm thinking
1.one way valve on the map
2.vortec 12to1 fmu
3.19lb/hr injectors


am i missing anything? i am not looking to build a race car just want a little more wheel speed.

[sharpxmen]

what size pipe would be best for routing under the oil pan to the passenger side mounted turbo?
i plan on using the stock manifold and wrapping the pipe in header wrap.

for fuel i'm thinking
1.one way valve on the map
2.vortec 12to1 fmu
3.19lb/hr injectors


am i missing anything? i am not looking to build a race car just want a little more wheel speed.

1. no way - you will end up with vacuum behind the valve when you open the throttle as it will close, it will not work - you are thinking of keeping the boost out of the map but at idle for example your map will see only vacuum, once you open the throttle the pressure in the intake will be higher that the one between the valve and the MAP sensor so it will close the valve, your MAP will still read the vacuum that you had at idle and nothing past that.
2. i'd say no, use a programmable MAP or you'll end up messing with your fuel and not get anywhere unless you only target your peak rpm (not to mention spending money a few times over and in the end going this route) - you will also need to get a larger fuel pump rated for that pressure and that still delivers the flow - the 12:1 will increase the pressure so much that your injectors could also start squirting instead of atomizing if you are too far off their rated pressure. You will find at some point that you need a different ratio diaphragm for that FMU and you will end up spending another $50 for a new one not to mention if you need to do it again.
3. way too small, but that depends on your boost and the fact that you won't use that vortec FMU so this comment is not applicable if you do - keep in mind that you need to account for the difference in the mass of air as well as the bsfc for a turbo which if i remember correctly is 0.6 vs 0.5 for a normally aspirated engine. Use a horsepower or turbo calculator to determine the required size of your injectors.

imo is best to start from what is your desired boost and calculate your injector size, get a programmable MAP and an adjustable FPR and fine tune it that way

[dwtaylorpdx]

what size pipe would be best for routing under the oil pan to the passenger side mounted turbo?
i plan on using the stock manifold and wrapping the pipe in header wrap.

for fuel i'm thinking
1.one way valve on the map
2.vortec 12to1 fmu
3.19lb/hr injectors


am i missing anything? i am not looking to build a race car just want a little more wheel speed.

I'd use a TJ exhaust pipe as a model but use heavy wall tubing (stainless if possible) for the
pipe and weld-ells for the turns. (Weld-ells are available at industrial plumbing stores.)
Don't be surprised when the exhaust manifold cracks, the stock unit is a wimpy POS.
It will probably crack on the back side between 2 & 3.

I totally get the idea to keep it on the cheap side, but be realistic,
Keep the boost down if your not running a really good EMU, and not
putting pistons and rods in.. Also, the 2.5 crank is not a huge piece,
they kept it light for economy.

For bottom end a custom header and pipe setup would likely work a little better but cost $$.

Dave

[lilbluej]

i'm a cheap ass but not a super cheap ass, i know i gotta pay to play.

i thought i read on here in someone's turbo thread that it runs the best with the 12to1 fmu and 19lb/hr injectors thats what i remember but i can't find the thread or the post.

i have a fuel cell with a after market HP efi pump so i dont think it will have a problem with the pressure. with the 12to1 and 5 or 6 pounds of boost i will have 60 or 70 psi at the rail. i'm gonna find that calculator.

the one way valve could have a relief hole drilled into it but dosn't the computer yank timing when the MAP is reading atmosphere? so wouldn't having some vacuum trapped in there make it run a little better.

[lilbluej]

its looking like the 12 to 1 with 24lb/hr injectors might be better.




this smilie kicks arse 

[sharpxmen]

i'm a cheap ass but not a super cheap ass, i know i gotta pay to play.

i thought i read on here in someone's turbo thread that it runs the best with the 12to1 fmu and 19lb/hr injectors thats what i remember but i can't find the thread or the post.

i have a fuel cell with a after market HP efi pump so i dont think it will have a problem with the pressure. with the 12to1 and 5 or 6 pounds of boost i will have 60 or 70 psi at the rail. i'm gonna find that calculator.

the one way valve could have a relief hole drilled into it but dosn't the computer yank timing when the MAP is reading atmosphere? so wouldn't having some vacuum trapped in there make it run a little better.

Sean dropped the FMU and got a split second PSC. but if you only target the top range when you are in high boost most of the time you have more chances of success. i think (but not sure) that he end up using 21 or 22lb/hr injectors and an adjustable hesco FPR.

i'm not sure how it works but i think you add the FMU pressure to your stock pressure (again, i'm not sure so you might be right and i got it wrong). put your numbers in and then come up with the required pressure - you need the following:
1- top boost, and from here the resulting HP
2 - injector flow to HP calculator - you will need to use 0.6 bsfc and the HP from #1 above (the bsfc is not accurate but an approximate value - for normally aspirated is 0.5) - from here you will determine the required injector flow at top boost/power
3 - injector flow at your resulting fuel pressure using your FMU - find an injector flow to fuel pressure calculator and put in your top pressure uning your FMU as your starting pressure and use 43.5psi as the target pressure. Use the required injector flow from #2 as your starting flow and it will calculate the injector flow required at 43.5psi (or 3 bar) - most injectors are rated at 43.5psi - from here you determine the injector you need. If you find an injector that is rated at a different pressure then use the same calculator to see if it is what your requirements are.

the MAP - no, you need to read the manifold pressure, otherwise it will always show the same reading rendering the input from MAP useless

if you have a hole drilled then there's no point in having it as it will not separate the 2 pressure areas, but then again, not using that valve + the FMU is the whole idea and it might work ok for what you need since it won't be a daily driver.

[dwtaylorpdx]

I forgot one thing, the valve you need is called a bypass not a blow-off valve,
the difference is the bypass valve allow the engine to suck air until the turbo
spins up, it allows air to bypass the turbo under vacume and re-circulates the
air in blow-off mode., You can still use a blow off for sudden engine deacceleration
and vent to atmosphere if you want the sound... :)

Dave

[Jeffy]

I forgot one thing, the valve you need is called a bypass not a blow-off valve,
the difference is the bypass valve allow the engine to suck air until the turbo
spins up, it allows air to bypass the turbo under vacume and re-circulates the
air in blow-off mode., You can still use a blow off for sudden engine deacceleration
and vent to atmosphere if you want the sound... :)

Dave

pshoooo!     It's popular with the Initial D crowd.

[lilbluej]

so i don't need a blow off valve but a bypass valve will help with spool up.

plan to start putting this junk together after thanksgiving.

thanks for the help guys.

[dwtaylorpdx]

The bypass valve works the same it just vents back to the turbo intake and you lose the cool noise. :) lol....
You have two goals, one is to allow air into the motor without the turbo being a bottle neck (Bypass mode) the second
is to release pressure between the turbo and throttle body when you lift off the gas so the turbo is still
spinning at full speed when you hit the go pedal again. (Blow-off mode) you can use either a dual purpose
valve or two specialty valves one for each purpose. On race cars I have found its way easier than I would
have thought a few years ago to have too much power too quickly down low! Its NOT a good thing to
break the rear tires loose coming on to the straight, and loop the car into the wall.....

Dave