Rear mounted turbo? - Page 3 - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


DIY Turbo Discussion greddy on a 1.8? homebrew kit?

Reply
 
 
 
LinkBack Thread Tools
Old 04-30-2008, 03:22 AM   #41
Murderator
iTrader: (76)
 
18psi's Avatar
 
Join Date: Apr 2008
Posts: 36,174
Total Cats: 2,575
Default

haha o **** didnt even think about how fucked up the intake piping would have to be on a setup like that good point
18psi is offline   Reply With Quote
Old 04-30-2008, 03:34 AM   #42
Junior Member
 
Join Date: Apr 2008
Location: Sacramento
Posts: 172
Total Cats: 0
Default

Which reminds me, rear turbo on a miata +1 for the bad idea. You mention not needing an intercooler because the charge air cools as it heads up to the motor anyways, but it also works against you because there is not a lot of exaust gasses to spool the turbo as is. Why let them cool that much before getting to the turbo? And throttle response will be *****
J.T. is offline   Reply With Quote
Old 04-30-2008, 04:00 AM   #43
Junior Member
 
Join Date: Mar 2008
Location: Hawaii
Posts: 53
Total Cats: 0
Default

Quote:
Originally Posted by J.T. View Post
...And throttle response will be *****
The rules are different with forced induction. Charge pipe length has almost no effect on throttle response.
2kBlk is offline   Reply With Quote
Old 04-30-2008, 04:07 AM   #44
Murderator
iTrader: (76)
 
18psi's Avatar
 
Join Date: Apr 2008
Posts: 36,174
Total Cats: 2,575
Default

Quote:
Originally Posted by 2kBlk View Post
The rules are different with forced induction. Charge pipe length has almost no effect on throttle response.
i disagree
18psi is offline   Reply With Quote
Old 04-30-2008, 04:08 AM   #45
Junior Member
 
Join Date: Apr 2008
Location: Sacramento
Posts: 172
Total Cats: 0
Default

Quote:
Originally Posted by 2kBlk View Post
The rules are different with forced induction. Charge pipe length has almost no effect on throttle response.
With your research, you, my friend, need a book called Maximum Boost by Corky Bell.

On another note, both throttle response and turbo lag will increase greatly by adding a lot more piping(although given a miata isn't THAT long, its still a good amount more piping).

Last edited by J.T.; 04-30-2008 at 04:36 AM. Reason: grammar >me
J.T. is offline   Reply With Quote
Old 04-30-2008, 11:34 AM   #46
Elite Member
iTrader: (3)
 
Join Date: May 2006
Location: Houston, TX
Posts: 2,900
Total Cats: 0
Default

Ummm... I'm pretty sure that maximum boost says charge piping doesn't make a whole lot of difference unless you stretch it into the next county. been a while since I read it though.
Arkmage is offline   Reply With Quote
Old 04-30-2008, 11:42 AM   #47
Senior Member
iTrader: (5)
 
Join Date: Nov 2007
Location: Troy, MI
Posts: 860
Total Cats: 13
Default

JT and 18psi, how tough do you think it is for Subaru to switch the position of the intake and exhaust ports on the cylinder head.........not very. With that they could have drastically shortened exhaust manifolding and also run a front mounted intercooler very easily.

Even with all those advantages they still didnt do it. I think its beyond me and you to speculate why. I'll take Corky's approach and say that Subaru knows a thing or two more about turbocharging than any of us here. Hence nothing wrong in copying their layout and giving it a shot.

Speculating that one layout or the other is "*****" and "crap" without trying it, IMO, is stupid. But hey, no harm in following convention for the majority of us.
The_Pipefather is offline   Reply With Quote
Old 04-30-2008, 11:43 AM   #48
Elite Member
iTrader: (39)
 
Zabac's Avatar
 
Join Date: Sep 2007
Location: High Point NC
Posts: 4,854
Total Cats: 8
Default

Once the charge pipes is pressurized it has no affect, it may take a millisecond longer to pressurize in a rear mount situation. The delayed spool happens due to exhaust gases cooling of too much before reaching the turbo, loss of heat=loss of energy, so you need mroe exhausts gases to have same spool. End of story.
Zabac is offline   Reply With Quote
Old 04-30-2008, 01:41 PM   #49
Junior Member
 
Join Date: Apr 2008
Location: Sacramento
Posts: 172
Total Cats: 0
Default

Quote:
Originally Posted by The_Pipefather View Post
JT and 18psi, how tough do you think it is for Subaru to switch the position of the intake and exhaust ports on the cylinder head.........not very. With that they could have drastically shortened exhaust manifolding and also run a front mounted intercooler very easily.

Even with all those advantages they still didnt do it. I think its beyond me and you to speculate why. I'll take Corky's approach and say that Subaru knows a thing or two more about turbocharging than any of us here. Hence nothing wrong in copying their layout and giving it a shot.

Speculating that one layout or the other is "*****" and "crap" without trying it, IMO, is stupid. But hey, no harm in following convention for the majority of us.

I didnt say the setup was ***** or crap I said throttle response and or turbo response.
And to put the intake underneath would not work out too well, there isn't that much room under there(don't tell me there is I stand under them for 6+ hours a day. Plus where you gonna put the oil pan with that intake under there? It would likely take a strange setup with some really awkward super unequal runners. And 18psi knows a thing or two about subies too

Anyways, it might be able to be done with a dry sump system, but they weren't trying to make a super expensive supercar.

Quote:
Once the charge pipes is pressurized it has no affect, it may take a millisecond longer to pressurize in a rear mount situation. The delayed spool happens due to exhaust gases cooling of too much before reaching the turbo, loss of heat=loss of energy, so you need mroe exhausts gases to have same spool. End of story.
The small turbo it will take to get decent responce would take noticbly longer to fill up 10+ feet more piping(rough estimate IDK how much there is). But if you had a big turbo back there then yea, it wouldn't take much longer to do so, but it would take EVEN LONGER to spool since the exhaust has cooled so much and we all know how turbo responce is generally related to sizes
J.T. is offline   Reply With Quote
Old 04-30-2008, 03:04 PM   #50
Elite Member
iTrader: (9)
 
Saml01's Avatar
 
Join Date: Jul 2007
Location: NYC
Posts: 5,730
Total Cats: 2
Default

Saml01 is offline   Reply With Quote
Old 04-30-2008, 03:27 PM   #51
Boost Pope
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago (Over two miles from Wrigley Field. Fuck the Cubs. Fuck them in their smarmy goat-hole.)
Posts: 26,317
Total Cats: 1,914
Default

The "next county" comment is directed specifically at speed-density based ECUs where no AFM/MAF is used.
Quote:
Originally Posted by Corky Bell in Maximum Boost
It is distinctly possible to upset the basic throttle response if an engine is equipped with an airflow meter positioned too far from the throttle body, Opening the throttle causes a low-pressure pulse to be created that travels up*stream toward the airflow meter, The time it takes this pulse to reach the flow-meter and cause it to react is indeed the delay in throttle response. Typically, such a pulse must travel from the throttle body to the intercooler, through the intercooler, back to the turbo, then to the flowmeter, in order for the flowmeter to register a response. It is not until the flowmeter receives this pulse that the air/fuel ratio can change to account for new load conditions in the engine. I should point out that there are exceptions here, based on the style of throttle-position sensor with which the engine is equipped. Nonetheless, it is generally true that the farther the throttle is from the airflow meter, the poorer the throttle response. Thus, this path length should receive some consideration in the design process.

When an engine is equipped with a speed density type of EFI system, wherein no airflow meter is utilized, or a blow-through carbureted turbo system, the length of the intake tract tan extend into the next county with no negative re*sults insofar as throttle response is concerned.

The overall problem in designing an intercooler system, then, lies in maximizing the ability of the system to remove heat from the compressed air while not adversely affecting boost pressure, losing throttle response, or contributing to any delay in boost rise.
Joe Perez is offline   Reply With Quote
Old 04-30-2008, 03:38 PM   #52
Junior Member
 
Join Date: Apr 2008
Location: Sacramento
Posts: 172
Total Cats: 0
Default

Quote:
Originally Posted by Joe Perez View Post
The "next county" comment is directed specifically at speed-density based ECUs where no AFM/MAF is used.
Quote:
Originally Posted by Corky Bell in Maximum Boost
It is distinctly possible to upset the basic throttle response if an engine is equipped with an airflow meter positioned too far from the throttle body, Opening the throttle causes a low-pressure pulse to be created that travels up*stream toward the airflow meter, The time it takes this pulse to reach the flow-meter and cause it to react is indeed the delay in throttle response. Typically, such a pulse must travel from the throttle body to the intercooler, through the intercooler, back to the turbo, then to the flowmeter, in order for the flowmeter to register a response. It is not until the flowmeter receives this pulse that the air/fuel ratio can change to account for new load conditions in the engine. I should point out that there are exceptions here, based on the style of throttle-position sensor with which the engine is equipped. Nonetheless, it is generally true that the farther the throttle is from the airflow meter, the poorer the throttle response. Thus, this path length should receive some consideration in the design process.

When an engine is equipped with a speed density type of EFI system, wherein no airflow meter is utilized, or a blow-through carbureted turbo system, the length of the intake tract tan extend into the next county with no negative re*sults insofar as throttle response is concerned.
The overall problem in designing an intercooler system, then, lies in maximizing the ability of the system to remove heat from the compressed air while not adversely affecting boost pressure, losing throttle response, or contributing to any delay in boost rise.

Thank you. Exactly what I've been trying to say, but couldn't find the passage. And anyways, when your out of boost and driving on the street your engine will be acting like a non turbo motor anyways.
J.T. is offline   Reply With Quote
Old 04-30-2008, 03:57 PM   #53
Senior Member
iTrader: (5)
 
Join Date: Nov 2007
Location: Troy, MI
Posts: 860
Total Cats: 13
Default

Actually, the quoted passage disagrees with what you said:

Quote:
Originally Posted by J.T. View Post
On another note, both throttle response and turbo lag will increase greatly by adding a lot more piping
Because everyone who is making decent power here runs a speed-density system, not the AFM.

BTW I wasnt alluding to you when I made that "*****" and "crap" statement.

The point is, unless someone tries this setup (near the cat, not near the muffler), speculating on its performance is of no consequence.
The_Pipefather is offline   Reply With Quote
Old 04-30-2008, 04:36 PM   #54
I'm Miserable!
iTrader: (5)
 
Join Date: Sep 2005
Location: SLC, Utah
Posts: 1,591
Total Cats: 0
Default

Quote:
Originally Posted by Saml01 View Post
The term white trash comes to mind, could that guy sound any more dorky??
zoom2zoom is offline   Reply With Quote
Old 04-30-2008, 04:40 PM   #55
Elite Member
iTrader: (39)
 
Zabac's Avatar
 
Join Date: Sep 2007
Location: High Point NC
Posts: 4,854
Total Cats: 8
Default

I bet you that's a member here that still has not come forward to tell us he is using a rear mount for fear of Epic Flamage
Zabac is offline   Reply With Quote
Old 04-30-2008, 04:41 PM   #56
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,838
Total Cats: 1,787
Default

Quote:
Originally Posted by Zabac View Post
I bet you that's a member here that still has not come forward to tell us he is using a rear mount for fear of Epic Flamage

he was banned here before your time.
Braineack is offline   Reply With Quote
Old 04-30-2008, 05:08 PM   #57
Miotta FTW!
iTrader: (24)
 
Splitime's Avatar
 
Join Date: Jun 2006
Location: Chicagoland, IL
Posts: 4,292
Total Cats: 26
Default

Quote:
Originally Posted by Braineack View Post
he was banned here before your time.
That really was an unfortunate day....


BWAHhhhahahahahahaha
Splitime is offline   Reply With Quote
Old 04-30-2008, 05:27 PM   #58
Elite Member
iTrader: (39)
 
Zabac's Avatar
 
Join Date: Sep 2007
Location: High Point NC
Posts: 4,854
Total Cats: 8
Default

Links? Was it Epic though?
Zabac is offline   Reply With Quote
Old 04-30-2008, 05:35 PM   #59
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,838
Total Cats: 1,787
Default

Quote:
Originally Posted by Zabac View Post
Links? Was it Epic though?
he tried to convince us rear mounting is superior in ever aspect. so i got tired of it and banned him.

I did love his comments like (from his tuning video on youtube) "ran autotune on spark map last night, so that's worked out" 3:00



watch at the end in "boost" slowest 15psi ive ever seen, in matters of spool and speed of car.
Braineack is offline   Reply With Quote
Old 04-30-2008, 05:54 PM   #60
Elite Member
iTrader: (39)
 
Zabac's Avatar
 
Join Date: Sep 2007
Location: High Point NC
Posts: 4,854
Total Cats: 8
Default

wow, looks like a total 'tard, that car moves abuot as fast as my stock 1.8.
Looks like the kinda guy who never had friends, and still doesn't.
Zabac is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Another Cast Manifold Corky Bell Prefabbed Turbo Kits 18 11-22-2016 10:01 PM
3rd Time's a Charm...hopefully. zephyrusaurai Meet and Greet 2 09-28-2015 11:59 PM
WTB 90-97 miata low profile headlight kit DonPlatt WTB 0 09-25-2015 03:57 AM


Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 12:32 PM.