Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Forums > Porsche Forums > Porsche 924/944/968 Technical Forum


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
Registered User
 
Join Date: Jul 2004
Location: Texas...all of it.
Posts: 782
Send a message via AIM to Makenzie71 Send a message via Yahoo to Makenzie71
Interesting experiment...

I come from the world of RX-7's...got into Supras...then decided I wanted back into RX-7's and somehow ended up with a Porsche....go figure. Anyways...RX-7s intentionally burn a noticeable amount of oil in the combustion chambers to keep everything lubed up. This leaves carbon deposites and such building in various places and gums up this and fouls that and what have you. Sometimes people will pull a vacuum hose and run it directly into a couple cups of water. Rotary engines will NOT hydrolock no matter how much fluid you put in them so basically what it does is introduce an amount of water to an incredibly hot enviroment...which steam cleans your combustion chambers...kinna. You can't really do this with a boinger because they will hydrolock. You have to run a combustable substance through.

Marvel Mystery Oil is another substance that people tend to pour into the rotary's vac system. So I thought I'd give it a shot in the 944. I pulled a vac line off some solinoid near the brake booster and stuck in a 14oz bottle of MMO and set the idle at about 2K rpm. She sputtered and near stalled and bucked and spit and coughed and shot out al kinds of smoke for a couple minutes. Once she drank all the MMO, I stuck vac line back where it was supposed to go, reset the idle, and played.

Throttle response (accel) is vastly imprved but my decel still seems to stick, and she accellerates much more smoothly. I suggest you guys with older engines do some experimenting.

__________________
http://forums.pelicanparts.com/uploa...1093905626.jpg

the "baby" that comes first...
Old 10-17-2004, 03:31 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
Registered User
 
scheistermeiste's Avatar
 
Join Date: Jul 2003
Location: Cincinnati, OH
Posts: 1,025
Send a message via AIM to scheistermeiste Send a message via Yahoo to scheistermeiste
doing it with my 7 is one thing, but ive hydrolocked a piston engine before and its not something i think i wanna try on my 24...
__________________
Special Edition 924S 1988 <- SOLD!

Asking if you should replace that timing belt is like asking if you should re-use a condom that may have in hole in it with a hooker.
Old 10-17-2004, 03:35 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
Registered User
 
Join Date: Jul 2004
Location: Texas...all of it.
Posts: 782
Send a message via AIM to Makenzie71 Send a message via Yahoo to Makenzie71
That's why you set the idle up or have someone rev the engine. You can't really hydrolock on the amount pulled in by one of those little vac lines, anyways. You also use a combustable substance like EFI cleaner or MMO so that any excess will burn out.
__________________
http://forums.pelicanparts.com/uploa...1093905626.jpg

the "baby" that comes first...
Old 10-17-2004, 03:39 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)
Registered User
 
Join Date: Feb 2003
Location: SF East Bay
Posts: 1,854
Hmm, I suspect throttle-response and power is a function of generated in the combustion chambers. How does having some carbon in the cambers affect how the air-fuel mixture burns? On engines with lots of carbon buildup, you actually have enough to increase compression, thus leading to more power.

Now on the older cars I've had, a 1st. gen RX-7, Celica, 240Z and numerous motorcycles, the carbs do get gummed up over time. Various vacuum jets and fuel passages gets clogged and the floats gets sticky. This leads to improper air-fuel ratios and poor throttle-response. Using a fuel-system cleaner like putting in some Marvel oil or Techron does indeed clean out the carbs and leads to improved throttle-response and power. I'm not so sure on modern fuel-injected car since they never get that dirty.

I run water-injection in my 951 which keeps everything nice and clean. Although the last five 951 and four 944 engines I've pulled apart this past year has had very little carbon build-up; less than 1 gram total.

It takes at least a 5-10% difference in power before your SOTP dyno feels it. If you can feel it, then that power-difference will definitely show up on a dyno-chart. If anyone wants to give me before and after dyno-charts that shows running Marvel oil through your engine provides measurable benefits, I'll pay for the dyno-runs.
Old 10-17-2004, 03:50 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
Registered User
 
Join Date: Jul 2004
Location: Texas...all of it.
Posts: 782
Send a message via AIM to Makenzie71 Send a message via Yahoo to Makenzie71
I doubt it gave me an increase in power...it did even out my throttle, though. Don't know why...just have to assume it's as a result...
__________________
http://forums.pelicanparts.com/uploa...1093905626.jpg

the "baby" that comes first...
Old 10-17-2004, 03:53 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)
Moderator
 
AFJuvat's Avatar
 
Join Date: Feb 2001
Location: Viera FL
Posts: 5,643
What you have described is an old trick to decarbon an engine. Yes, it does work in 944s. Though you usually use the brake booster vacuum line and you use a second person to keep the car running while the other introduces the water into the system.

It works very well, particularly on the 16V motors that are more prone to carbon build-up.

This procedure is NOT recommended unless you know what you are doing. If you are not careful, you WILL hydrolock the motor.

AFJuvat
__________________
Es geht nicht darum wie schnell man faehrt, sondern wie gut man schnell fahren kann.

Ihr Brunnen der nutzlosen Porsche Information
Old 10-17-2004, 06:36 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #6 (permalink)
 
952 952 is offline
Banned
 
952's Avatar
 
Join Date: Apr 2004
Location: I love the U.S.A
Posts: 552
Danno, are you running port injection or in the IC to TB pipe? Home made kit? Or Aquamist / Snow job?
Old 10-17-2004, 07:51 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #7 (permalink)
Registered User
 
Join Date: Feb 2003
Location: SF East Bay
Posts: 1,854
I've been working with a local engineer on developing a water-injection kit. It has both external intercooler-spray(2-nozzles) and port-injection of water near the injectors (4 separate nozzles). The idea is to have the water go into the combustion chambers as liquid rather than vapor to displace as little air as possible. Then on the compression-stroke, the heat vaporizes the water which then cools the mixture down.

The only reservation I had was the rates of heat build-up on the compression-stroke vs. the rate of cooling from the water. Obviously having to vaporize and absorb heat on a compression stroke gives much less time than spraying it into the intercooler pipe and having it cool the air on its way in. I'm sure there's some engineering FEA packages that might be able to model this, but I'll go with imperical testing for now.

So far it's working out alright at a 2-gal/hour injection rate under full-throttle with a pressure-activated switch. But I'm working on a progressive controller that'll let me use a 3D map to control the water based upon BOOST x RPM. I'm finding that the initial spray of water at 13ps is too much at low RPM, but not enough at high RPM. But it does allow me to run 25psi on a stock 2.5L using 89-octane gas.

Last edited by DannoXYZ; 10-18-2004 at 01:28 PM..
Old 10-18-2004, 01:07 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #8 (permalink)
Registered User
 
fast924S's Avatar
 
Join Date: Jun 2003
Location: New Haven, CT
Posts: 3,348
Garage
Send a message via AIM to fast924S
We do the same thing at toyota, using a BG air induction cleaner, Pull a vaccum line while the engine is around 3,000rpm and let then engine pull in the cleaner, cleansthe intake runners, valves and combustion chamber very well, O2sensor and cat safe, If you think about it with all the emissions stuff there is alot of dirty air that the engine is sucking in that can build up in the runners and throttle body, even carbon depsites on the valves.

Now as for letting your engine build up carbon for more power I dont think its a good idea, flow rates will change, a/f ratio will change, temps will change and it wont be even threw each cylinder. Keep these babies clean they like it that way

__________________
1986 951, Stock for now.
]87 924S Gaurds red- SOLD after 11 years of ownership
Old 10-18-2004, 02:14 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #9 (permalink)
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 


All times are GMT -8. The time now is 03:00 AM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2020 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.