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Author Topic: boost is boost??  (Read 18037 times)
347HO
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« Reply #15 on: August 14, 2009, 01:33:37 pm »

Damn, a pop quiz.   
I was just saying that you can 15psi on the same setup w/ 2 different turbos and one could very well be much faster than the other due to the variables involved.

Just sayin'  Wink


I think we're all pretty much on the same page Matt.
After conferring with Jay during our morning chat...  15psi is in fact 15psi no matter the size of the turbine BUT;
15psi @ 90*f is not the same as 15psi @ 300*f.  There will be a considerable "delta P" in air density.
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... it was REALLY revving at like 4K...
If I saw that thing in my rear view Im pulling over to let you by, I be scared of that thing Huh? i dont know wich car is uglier ur or mine?
Javier
Ugly?  Easy now -- that's my baby and it's got lots of unique character!  When I drop that built 445" stroker in it you won't have any time to "pull over to let me pass" because I'll have already blown past you when you figure out what the hell was that loud noise behind you . . .  
Dono
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« Reply #16 on: November 29, 2013, 02:21:02 pm »

Guys, I'm going to bump this....
I'm currently planning a rear mount custom turbo (302, bone stock) and I have another question on 15psi being 15psi.

Assuming temperatures are the same, what about a difference in lower and upper intake volume?

I'm still trying to wrap my head around boost as compared to N/A.  Following 15psi being 15 psi, the difference in lower and upper intake volume would not make a difference.  Whats everyones thoughts on this?  I know boost changes the rules quite a bit.

I'm thinking of not worrying about porting the upper and lower intakes, as there wouldn't be any real gain under boost.
Also, I'm questioning using either 2 inch, or 2.5 inch cold side piping from the spare tire where the turbo will be.  I think the smaller 2 inch cold side piping to the throttle body would give me the 15psi faster as the volume on the cold side would compress faster (Less lag?).

Anyway, I do have a plan in place for fuel system, blow thru pro-m slot maf, tuning, ect.  I just want to focus on cold side volumes. 



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2000 Ford Explorer 5.0 w rear mount turbo
347HO
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« Reply #17 on: November 29, 2013, 04:23:01 pm »

In my experience, you'll want to keep your port volumes to continuously be greater from the intake valve to the intake plenum.
Without knowing what your engine needs...  can't know what volume it will consume in one complete cycle at a given rpm and load.
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... it was REALLY revving at like 4K...
If I saw that thing in my rear view Im pulling over to let you by, I be scared of that thing Huh? i dont know wich car is uglier ur or mine?
Javier
Ugly?  Easy now -- that's my baby and it's got lots of unique character!  When I drop that built 445" stroker in it you won't have any time to "pull over to let me pass" because I'll have already blown past you when you figure out what the hell was that loud noise behind you . . .  
Dono
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« Reply #18 on: November 29, 2013, 05:55:13 pm »

Thanks for the response.  Appreciated.

I think I'll be ok with no porting.
I have to remember that I have a stock 302 (2000 Ford explorer) that is having a rear mount on it and an air/water intercooler mounted on the frame rail as the cold side comes up front.

My needs are simple, as I will have motor issues, and then transmission issues if I start pushing past around 6-8 psi.

I'll get the turbo working and if the project is a success, I'll start looking at costs of a forged motor from Woody with a upgraded trans.  60lb injectors are going in, so there will be room to grow.  That's a long way off though, and might not ever get there.

Back on topic, I was trying to figure out the best way to keep cold side volume down for less lag.  My turbo is a t4 72mm turbine with a f1-68 compressor blade, so it should still spool ok from back there.

I'll post how I'm making out in the appropriate forum in spring when the pieces are put together.
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2000 Ford Explorer 5.0 w rear mount turbo
CDW6212R
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« Reply #19 on: November 29, 2013, 06:23:42 pm »

Thanks for the response.  Appreciated.

I think I'll be ok with no porting.
I have to remember that I have a stock 302 (2000 Ford explorer) that is having a rear mount on it and an air/water intercooler mounted on the frame rail as the cold side comes up front.

My needs are simple, as I will have motor issues, and then transmission issues if I start pushing past around 6-8 psi.

I'll get the turbo working and if the project is a success, I'll start looking at costs of a forged motor from Woody with a upgraded trans.  60lb injectors are going in, so there will be room to grow.  That's a long way off though, and might not ever get there.

Back on topic, I was trying to figure out the best way to keep cold side volume down for less lag.  My turbo is a t4 72mm turbine with a f1-68 compressor blade, so it should still spool ok from back there.

I'll post how I'm making out in the appropriate forum in spring when the pieces are put together.

Include a new set of exhaust manifolds from the start for the project. A turbo system doesn't benefit much at all from great headers, but it does suffer greatly if the exhaust is very restrictive.

The OEM manifolds on any 302 Explorer suck, they are not worthy of being on a 3.0 liter engine, loet alone a boosted 5.0 engine. Save your money from buying any other manifolds, $600-$700 is not worth it for those also too small headers. Find someone to make you a simple log manifold set for that project. Anyone good at doing the turbo pipes can build nice log manifolds for the heads. that alone should gain a lot of free power versus the stock manifolds, or the TM junk.

I wish you well on that, I gave up on the idea of a turbo, I couldn't see a way to get the air cleaner under the hood with a remote turbo.
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Don

1991 Mark VII LSC Special Edition, soon to be OBDII and 4R70W, then GTC body kit and 347.
1998 Mountaineer, plans for A4WD and KB 2200 blower later, XP8 parts, paint and a 332.
1973 Ranchero and 72 Sport front end ...will be a 351 Clevor, EFI and 4R70W.
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« Reply #20 on: November 29, 2013, 07:34:28 pm »

Great to see you here!  I'm lurking, trying to get solid info to avoid mistakes.
Thanks for the manifold tip.  I'll look for some manifold flanges and see what kind can do.
On the air filter, I'm thinking an aluminum garbage can, or a plate hiding the filter from the road.....
It will be interesting, that's for sure.
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2000 Ford Explorer 5.0 w rear mount turbo
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« Reply #21 on: November 30, 2013, 11:32:20 am »

For a rear mount on the thrifty side why not run some cheap long tubes and 2 1/4 exhaust?
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« Reply #22 on: November 30, 2013, 02:56:36 pm »

Im guessing 2 1/4 is the least expensive?  That takes care of my question of going either 2 or 2 1/2.  Thanks Jay.  The smaller pipe will keep intake volumes down, along with an air water intercooler so the air takes less time to compress.   Stainless steel exhaust pipe will last a very long time.
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bikefreak600
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« Reply #23 on: November 30, 2013, 08:46:28 pm »

15psi vs 15psi IS NOT the same.  psi does not factor in volume.  the myth that psi builds horsepower is misleading. the only reason more psi= more power is because the impeller is spinning faster, resulting in moving more volume of air.  
real dyno numbers, stock engine w/ e85 supra tuned at sound performance. only change was turbo.
51mm turbo 31psi = 667rwhp 700lbtq.  this turbo was maxed out, could not make anymore boost
66mm turbo 31psi = 700rwhp 680lbtq   this turbo is capable of 40+ psi.  lots of power left.
 did not want to go higher fear of lifting head studs again.
 the bigger turbo made more power ever where over 19psi... minus a spike in peak torque w/ smaller turbo
 also the addition of a quick spool turbo maniflod the bigger turbo made more low end tq, faster spool time as well.  actually the bigger turbo, car is still faster with boost controller at 24 psi.
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« Reply #24 on: November 30, 2013, 08:59:16 pm »

Boost is just one factor to create power. The heat in the air(IAT) is the other biggest factor, which drops with more efficient blowers and less restrictions.

The things which help power like the inlet sizing of parts does help, but it's not nearly as critical for a boosted engine.

The turbo can increase power a bunch in even a choked stock smallish engine combo like a stock 302. Improve the same things to make more power of course, but the effect is just a little different.

That smaller turbo example above put more heat into the air charge, at the 31psi. The larger turbo at the same psi didn't create as much heat, it works more efficiently on that engine, thus more power.
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Don

1991 Mark VII LSC Special Edition, soon to be OBDII and 4R70W, then GTC body kit and 347.
1998 Mountaineer, plans for A4WD and KB 2200 blower later, XP8 parts, paint and a 332.
1973 Ranchero and 72 Sport front end ...will be a 351 Clevor, EFI and 4R70W.
347HO
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Location: Seattle, Washington
I believe they landed on the moon.


« Reply #25 on: November 30, 2013, 10:28:56 pm »

15psi vs 15psi IS NOT the same.  psi does not factor in volume.  the myth that psi builds horsepower is misleading. the only reason more psi= more power is because the impeller is spinning faster, resulting in moving more volume of air.  
real dyno numbers, stock engine w/ e85 supra tuned at sound performance. only change was turbo.
51mm turbo 31psi = 667rwhp 700lbtq.  this turbo was maxed out, could not make anymore boost
66mm turbo 31psi = 700rwhp 680lbtq   this turbo is capable of 40+ psi.  lots of power left.
 did not want to go higher fear of lifting head studs again.
 the bigger turbo made more power ever where over 19psi... minus a spike in peak torque w/ smaller turbo
 also the addition of a quick spool turbo maniflod the bigger turbo made more low end tq, faster spool time as well.  actually the bigger turbo, car is still faster with boost controller at 24 psi.

I think I know what you're trying to say, however...  15psi is in fact 15psi, and the volume consumed does not matter as long as the pump can deliver 15psi at all operating rpm and load.

Boost is just one factor to create power. The heat in the air(IAT) is the other biggest factor, which drops with more efficient blowers and less restrictions.

The things which help power like the inlet sizing of parts does help, but it's not nearly as critical for a boosted engine.

The turbo can increase power a bunch in even a choked stock smallish engine combo like a stock 302. Improve the same things to make more power of course, but the effect is just a little different.

That smaller turbo example above put more heat into the air charge, at the 31psi. The larger turbo at the same psi didn't create as much heat, it works more efficiently on that engine, thus more power.
I know what you're saying, however "density altitude" has more impact than air temp.
For instance, an engine will deliver 100% at sea level and 75% power at 6000 feet.  Now factor in increased air temp and we will be more inefficient.
I simplified my explanation...  just so you know.
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... it was REALLY revving at like 4K...
If I saw that thing in my rear view Im pulling over to let you by, I be scared of that thing Huh? i dont know wich car is uglier ur or mine?
Javier
Ugly?  Easy now -- that's my baby and it's got lots of unique character!  When I drop that built 445" stroker in it you won't have any time to "pull over to let me pass" because I'll have already blown past you when you figure out what the hell was that loud noise behind you . . .  
CDW6212R
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« Reply #26 on: December 01, 2013, 11:35:58 am »

True Dale, density is very important and heat isn't always the second largest. It all matters, that's what we should be saying. Wink
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Don

1991 Mark VII LSC Special Edition, soon to be OBDII and 4R70W, then GTC body kit and 347.
1998 Mountaineer, plans for A4WD and KB 2200 blower later, XP8 parts, paint and a 332.
1973 Ranchero and 72 Sport front end ...will be a 351 Clevor, EFI and 4R70W.
347HO
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Big Block
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I believe they landed on the moon.


« Reply #27 on: December 01, 2013, 11:58:37 am »

It all matters, that's what we should be saying. Wink

Roge...   was just clarifying in case someone comes along and quotes you incorrectly.
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... it was REALLY revving at like 4K...
If I saw that thing in my rear view Im pulling over to let you by, I be scared of that thing Huh? i dont know wich car is uglier ur or mine?
Javier
Ugly?  Easy now -- that's my baby and it's got lots of unique character!  When I drop that built 445" stroker in it you won't have any time to "pull over to let me pass" because I'll have already blown past you when you figure out what the hell was that loud noise behind you . . .  
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