DIY_EFI Digest Monday, 8 March 1999 Volume 04 : Number 152 In this issue: Re: injector drivers Re: Which Intake Re: throttle before or after turbo Re: Which Intake Re: Which Intake Re: throttle before or after turbo Re: Which Intake suck or blow? See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- From: "John Dammeyer" Date: Sun, 7 Mar 1999 20:18:49 -0800 Subject: Re: injector drivers Hi Bruce, OK. I if I under stand this correctly, my algorithm should: a) Determine that TPS has changed. The amount of change suggests the degree of enrichment on the PW. Start a timer, user configurable during engine tuning or perhaps also based on delta TPS. b) Start checking delta MAP and when it stops changing, (within some guideline), back off on enrichment. This would suggest, for example, if engine at 14.7:1 and throttle hit hard, that an initial change of PW to give 10:1 for a time interval. Then, reduce to 12.6:1 once MAP sensor shows a change. Then, as MAP pressure reaches steady state back PW off until 14.7:1 is reached again. I'm in a situation where I have a fluid load (propeller) on the engine so at some point I will have WOT, maximum airflow at some RPM with hopefully a Ve approaching 1. Thanks, John - -----Original Message----- From: Bruce Plecan To: diy_efi@xxx.edu Date: Sunday, March 07, 1999 4:50 PM Subject: Re: injector drivers > >-----Original Message----- >From: John Dammeyer >To: diy_efi@xxx.edu >Date: Sunday, March 07, 1999 4:52 PM >Subject: Re: injector drivers > > >Delta TPS, and Delta MAP, both corrected by coolant temp., are common. >Bruce > >>I'm building a ignition/injection system for a Honda 1595 CC engine. So >>far the CD ignition works great as do all the appropriate sensors like >>the MAP/Air Temperature etc. I'm wondering how to go about handling the >>Throttle Position Sensor. >> >>ie: While the engine is in a steady state condition the combination of >>MAP and Barometric Pressure sensors along with RPM determine the initial >>injector pulse width. The O2 sensor closes the loop. Now if the >>throttle is opened suddenly I know I need to increase the pulse width. >> >>I can: >> >>1) just use a timer to increase the mixture to 10:1 for a preprogrammed >>time. This simulates the accelerator pump on a carburated engine. >> >>2) Increase the mixture to 10:1 until the ratio between MAP and >>Barometer reach some set point. >> >>3) Do both. >> >>What I don't want happening is a too rich mixture once the throttle is >>wide open and the engine is loaded at some RPM that no longer increases. >> >>Would I be best to use the rate of change of the RPM as an indicator to >>back off on the Pulse Width? >> >>What do the commercial injection systems do? >> >>Comments? >> >>Thanks, >> >>John >> > > ------------------------------ From: Dynacar@xxx.com Date: Sun, 7 Mar 1999 23:35:38 EST Subject: Re: Which Intake In a message dated 99-03-07 20:50:29 EST, you write: << the vacuum caused when closing the throttle quickly, is actually is easier on the turbo >> yes, this works ok, but the vacuum pulls a lot of oil into the system as soon as the seals age a little. You have to use a special turbo that can handle the vacuum. I used to have a Rajay (actually i still have it) which was made for draw-thru. Peter ------------------------------ From: Dynacar@xxx.com Date: Sun, 7 Mar 1999 23:47:14 EST Subject: Re: throttle before or after turbo In a message dated 99-03-07 23:37:34 EST, you write: << Old style carbureted turbos with draw thru carbs had decent throttle response but the volume of the intake was small, carb, turbo, manifold with no intercoolers, etc. If you have a high performance turbo with high boost and an intercooler, lots of plumbing, etc, you definitly need to have the throttle after the turbo. In that case, you also need a valve to prevent surging the turbo when closing the throttle after a high rpm run, say a shift. >> With an intercooler full of combustible mixture, won't the draw-thru setup be a bomb just waiting to explode on the next backfire thru an intake port? ------------------------------ From: "Bruce Plecan" Date: Mon, 8 Mar 1999 00:16:51 -0500 Subject: Re: Which Intake - -----Original Message----- From: Greg Hermann To: diy_efi@xxx.edu> Date: Sunday, March 07, 1999 10:37 PM Subject: Re: Which Intake Spend some time cleaning out intercoolers for a GN, and even post TBs load up with oil. The best way of using turbos is with deisels. No TBs. There are aftermarket boost controllers using "High Speed Stepper Motors" for dump valves, and even some using fuzzy logic. I can't imagine not being able to use a couple MAPS sensor fore+aft of the TB downstream of the turbo, and control the intake pressure during overrun. Use a EGR valve or IAC, or something like that. Bruce ------------------------------ From: DC Smith Date: Sun, 07 Mar 1999 23:37:19 -0600 Subject: Re: Which Intake Dynacar@xxx.com wrote: > > In a message dated 99-03-07 20:50:29 EST, you write: > > << the vacuum caused when > closing the throttle quickly, is actually is easier on the turbo >> > > yes, this works ok, but the vacuum pulls a lot of oil into the system as soon > as the seals age a little. You have to use a special turbo that can handle the > vacuum. I used to have a Rajay (actually i still have it) which was made for > draw-thru. I no longer have the draw though setup, but I can tell ya first hand, the post turbo TB doesn't stop the turbo from giving up oil. :) Got my intercooler off right now, and it's coated pretty good. The track opens in less than a month, I think I'll pull the turbo now and put a seal in it. I've seen both turbo's and the seal is no different from one type to the other. I've never heard anyone mentioning any difference in turbo seals before, although there may well be a difference I can't see. *********************************************************************** Dan Smith 84 Regal 12.13@112 GSCA# 1459 St.Charles, Missouri mailto:dcsmith@xxx.net mailto:dcsmith@xxx.org mailto:morepoweral@xxx.net mailto:morepoweral@xxx.org mailto:morepoweral@xxx.net mailto:smithd@xxx.com http://www.tetranet.net/users/morepoweral *********************************************************************** ------------------------------ From: bearbvd@xxx.net (Greg Hermann) Date: Sun, 7 Mar 1999 22:52:11 -0700 Subject: Re: throttle before or after turbo >Old style carbureted turbos with draw thru carbs had decent throttle >response but the volume of the intake was small, carb, turbo, manifold with >no intercoolers, etc. If you have a high performance turbo with high boost >and an intercooler, lots of plumbing, etc, you definitly need to have the >throttle after the turbo. In that case, you also need a valve to prevent >surging the turbo when closing the throttle after a high rpm run, say a >shift. > >Gary Derian Even with all of the above described plumbing, I doubt that the total volume of plumbing is more than two or three engine revolutions worth of air--so where is the problem with throttle response?? It was impossible to run an intercooler with a draw through carb because of mixture puddling problems. With port injection, no such problems. Greg > > >>At 12:32 PM 3/6/99 EST, WLundquist@xxx.com wrote: >> >>>A better alternative is to put the tb's before the turbo inlet >>>so that when the tb's are closed the turbo will spin in a vacuum and >maintain >>>rpm, this will make for guicker recovery when you stab the throttle. >> >>Frederic mentioned poor trailing-throttle response as a possible drawback >>to this approach... I personally don't believe that, for various >>reasons, but the thing I do worry about is having lots of oil sucked >>into the air in the turbo. How much of a problem is this, really? I >>know some turbo vendors have special sealing options avilable, but I'd >>like to hear from people who have set any old turbo up with the TB >>before it, if you had much problem with sucking oil into the intake. >> >>The only reason I care this week is a weird turn of events has led >>to the possibility that I'll get a turbo'ed car soon, and I'd like to >>know, if I move the throttle before the turbo, how much trouble am >>I asking for? Yeah I could get a new turbo/upgrade it/etc, but for >>various reasons I would not like to have to do that. >> >> TIA, >> Chris C. ------------------------------ From: bearbvd@xxx.net (Greg Hermann) Date: Mon, 8 Mar 1999 00:16:20 -0700 Subject: Re: Which Intake > I've seen both turbo's and the seal is no different from one type to >the other. I've never heard anyone mentioning any difference in turbo >seals before, although there may well be a difference I can't see. > Take a peek in the Turbonetics catalogue, for one--there are different types of seals available. The most expensive one, the "mechanical" seal, is the only way to go if you are doing a draw through. It will prolly help anything stay cleaner tho-- Regards, Greg ------------------------------ From: "Espen Hilde" Date: Mon, 8 Mar 1999 10:46:06 +0100 Subject: suck or blow? In my 69 NSU 1000 TT I had a the carb in front of turbo, it was a rayay f flow. The oil seal did go after a short while and the engine started using a LOT of oil.I wanted to fix the turbo but the experiance with the turbo repairer was that the seal it did not last long.I changed to blow trou and my experiance was that it was much better control with the trottle in the first carb in front of turbo system.On blow trou the trottle are seeing a sudden increase in density when the boost comes in and a lot more air is entering, sometimes the car acclerates more than you wish and you have to back of the trottle. In my oppinion the way of controlling the turbo engines output , shoud be a combination of trottle and a foot controlled wastgate.When you have wot ,the boost pressure could be 4psi with furter trottle movement the boost could be increased. An other way witch I think is decribed in mc Innes turbo book is to have 2 trottles one on each side of turbo.By adjusting the trottles you can deside if you want vacuum in turbo or not. Espen Hilde ------------------------------ End of DIY_EFI Digest V4 #152 ***************************** To subscribe to DIY_EFI-Digest, send the command: subscribe diy_efi-digest in the body of a message to "Majordomo@xxx. A non-digest (direct mail) version of this list is also available; to subscribe to that instead, replace "diy_efi-digest" in the command above with "diy_efi".