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4g61t 16g automatic need nitrous to get boost on launch?
http://www.4g61t.org/forum/viewtopic.php?f=6&t=38806		 Page 1 of 3
Author:  pyro719 [ Sun May 11, 2014 3:44 pm ]
Post subject:  4g61t 16g automatic need nitrous to get boost on launch?
I bought an 89 Summit yesterday with the 4g61t, 2 liter cams, small 16g E85, fic 1050's, ecmling v3 speed density, stock stall auto tranny with blue wire mod for full line pressure and road surge shift box. The car runs great but takes a while to boost and will not build any boost when power braking from a stop. Is this common with the 1.6 and 16g automatic combo? Will it need nitrous to leave the line on boost or is this something that can be done in the tune? I havnt looked at the tune yet and know my way around link ok just trying to get some input before I dig into it. First thing is boost leak test.
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Author:  thomcasey [ Sun May 11, 2014 5:29 pm ]
Post subject:  Re: 4g61t 16g automatic need nitrous to get boost on launch?
Go to the junkyard and get a vacuum pump from a late model vw or audi. Put it in place of the brake booster connection. This will allow you to brake boost. Should be able to launch with 15lbs
Author:  pyro719 [ Sun May 11, 2014 7:06 pm ]
Post subject:  Re: 4g61t 16g automatic need nitrous to get boost on launch?
I dont have a problem with pushing through the brakes I have a problem building boost
Author:  Jeremy Rothrock [ Sun May 11, 2014 9:40 pm ]
Post subject:  Re: 4g61t 16g automatic need nitrous to get boost on launch?
I believe you're talking about anti-lag? That would require some changes to the timing and fuel maps in DSMlink. Be very careful though. I've read you can waste a turbo pretty quickly by doing this a lot.
Nice ride BTW!
Author:  slowdsm [ Mon May 12, 2014 1:10 am ]
Post subject:  Re: 4g61t 16g automatic need nitrous to get boost on launch?
when u take of in 1st... about what rpm does it start to build boost..and when does it get full boost?... and on a 16g u do not need nos to spool it..

if the car is full boost by about 4k max.. its definatly the tune.. if it doesnt spool up till later then u have a boost leak or bad turbo..

I have a auto also.. with a 14b.. if it wont spool off the line then its in the tune.. when it was in my colt I could hit about 3200 rpms and 15 psi before letting off the brake..

same trans in my mirage but with a 1.6 motor and I cant get it to stall at all off the line.. but I know for a fact my tune is all jacked up on this car..





Steve
Author:  thomcasey [ Mon May 12, 2014 6:19 am ]
Post subject:  Re: 4g61t 16g automatic need nitrous to get boost on launch?
Quote:
I dont have a problem with pushing through the brakes I have a problem building boost
If you are not pushing through your brakes, then you aren't building boost :) The Vacuum pump will allow you to build tons of brake-boost at the line while maintaining braking. As stated above, something must be going on with the tune as 16g's build boost pretty fast.
Author:  pyro719 [ Mon May 12, 2014 10:21 am ]
Post subject:  Re: 4g61t 16g automatic need nitrous to get boost on launch?
Quote:
when u take of in 1st... about what rpm does it start to build boost..and when does it get full boost?... and on a 16g u do not need nos to spool it..

if the car is full boost by about 4k max.. its definatly the tune.. if it doesnt spool up till later then u have a boost leak or bad turbo..

I have a auto also.. with a 14b.. if it wont spool off the line then its in the tune.. when it was in my colt I could hit about 3200 rpms and 15 psi before letting off the brake..

same trans in my mirage but with a 1.6 motor and I cant get it to stall at all off the line.. but I know for a fact my tune is all jacked up on this car..





Steve
If I just wot it from a dead stop boost comes on around 3k rpm and full boost by 4,000 then it just blows the tires off I shift to second and spins threw second and into third. I'm going to boost leak test it and get it sealed up nice and tight and go from there. a/f ratio is hella fat at idle like 10.5/1. This may also be contributing to to the slow spool up and no boost off the line :yawinkle: Image
Author:  thomcasey [ Mon May 12, 2014 12:52 pm ]
Post subject:  Re: 4g61t 16g automatic need nitrous to get boost on launch?
Yea, that is a tiny filter
Author:  slowdsm [ Mon May 12, 2014 1:09 pm ]
Post subject:  Re: 4g61t 16g automatic need nitrous to get boost on launch?
if idle A/F is 10;5 u are super rich.. and I guarantee its the tune.. get it tuned and I bet it will be alot better.




Steve
Author:  thomcasey [ Mon May 12, 2014 2:18 pm ]
Post subject:  Re: 4g61t 16g automatic need nitrous to get boost on launch?
Yea, your idle for e85 should be closer to 15.1 with WOT around 12.1. Even pump 93 octane (what I run) I am @ 14.8 for idle and 10.5-1 WOT @ 22psi.
Author:  pyro719 [ Mon May 12, 2014 2:32 pm ]
Post subject:  Re: 4g61t 16g automatic need nitrous to get boost on launch?
Yeah I'm going to play with the tune after the boost leak test and a much bigger air filter. It cruises at 14.7 but idles Real rich. Ive also read that the automatics pull timing when you try to brake stall them So I will have to log it and see what the timings doing as well
Author:  CaptainTonus [ Mon May 12, 2014 5:06 pm ]
Post subject:  Re: 4g61t 16g automatic need nitrous to get boost on launch?
16g's on a 1.6L are pretty laggy, so this isn't too surprising. NOS would help, or a looser torque converter with a higher stall speed.
Quote:
\Ive also read that the automatics pull timing when you try to brake stall them So I will have to log it and see what the timings doing as well
If this is true, it would only be if the car was on a totally stock ECU/TCU. If you have ECMLink on there, it probably removed all of that BS, but I could be wrong. Is there still a TCU on the car, or was that removed?
Author:  Jeremy Rothrock [ Mon May 12, 2014 5:09 pm ]
Post subject:  Re: 4g61t 16g automatic need nitrous to get boost on launch?
You should really head over to dsmtuners and search anti-lag so you understand what you're dealing with. You will need more fuel and your timing should be retarded to the point that your creating combustion in the exhaust manifold and not the block. Beware again, the more boost you build, the turbo and related parts are more prone to failure.
Author:  Mechacode [ Mon May 12, 2014 5:46 pm ]
Post subject:  Re: 4g61t 16g automatic need nitrous to get boost on launch?
You should be able to build boost just by footbraking it with an auto. Something sounds fishy if it isn't.
Author:  CaptainTonus [ Mon May 12, 2014 6:04 pm ]
Post subject:  Re: 4g61t 16g automatic need nitrous to get boost on launch?
Quote:
You should be able to build boost just by footbraking it with an auto. Something sounds fishy if it isn't.
Have you ever tried doing it with a DSM auto trans? If the converter is stock and you don't have a lot of torque (i.e. 4g61t) then it is quite sluggish at lower RPM's. When I first bought my Mirage, it still had the 1.6 in it with a Big 16g, and it was AWFUL. It didn't go anywhere until like 5,000rpm. Granted, the engine had 50psi compression in one of the cylinders...
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