DIY_EFI Digest Thursday, May 27 1999 Volume 04 : Number 311 In this issue: Re: Ignition retard knock sensor. Re: O/T Compression ratio and supercharging Re: 7730 and dis Re: 94 Truck problem solved Re: O/T Compression ratio and supercharging Re: v8 block thread cleaning Re: Prowler V6 Re: Ignition advance, was Re: alternative engines, WARPED See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- Date: Wed, 26 May 1999 23:00:11 -0500 From: "G. Scott Ponton" Subject: Re: Ignition retard knock sensor. Hi all, I have been following this thread for a while. I am going to put my .02$ in at this point. I am sure some will have "alternate" views of this but ........................ >In the last few months, I've found that detonation is *not* directly >related to boost. On 89 octane and no water injection for instance, if >I whack the throttle open above about 2000 rpm, boost jumps almost >instantly to 5 - 6 psi. Detonation is almost instant as well. However, >if I ease into the throttle and let boost come up over 2 or 3 seconds, it >can go to 7 or 8 psi with no detonation. >Also, if I'm in a situation where I want to accelerate and I'm at say >3000 rpm in a high gear. I can press the throttle up to a certain point >(probably about 3/4) and get say 6 or 7 psi with no detonation. If I >then floor it, boost doesn't increase very quickly until the rpms come >up a bit (takes longer in high gear) and the mixture isn't going lean >according to the A/F meter, but detonation happens pretty much instantly. >Still can't figure that one out. Boost and A/F don't change very quickly, >but detonation seems to be tied directly to the gas pedal. The A/F ratio isn't the only thing happening here. Yes, you can use "extra" fuel to help cool the intake charge and to reduce detonation. It only works to a point though. After a certain point you are just pouring fuel out the t-pipe as the mixture becomes rich enough to be impervious to pre-ignition or any ignition for that matter. The reason you can "ease" into the throttle an let the boost climb slowly has to do with the density of the air charge. It works the same way with a NA engine which likes to "ping" at WOT. If you slowly step into it you reduce the density of the air charge and by the time you get to the higher revs the "time" it takes for the piston to move is reduced. Therefor, even though the cylinder pressures are "equal", the uncontrolled burn doesn't have time to create "ping" like it does at slower engine speeds. When you open the throttle suddenly to WOT you are imposing no restriction to the density of the air entering the cylinders. Boost won't necessarily climb quickly as it takes some time for the turbo to "spool up". If it spools up too quickly the housings are mismatched for the application and the waitgate will have to be a complete equal sized bypass to keep boost under control. My experience with late model engines is that they are tuned from the factory to be on the edge of pre-ignition. Add just 2 lb. boost and you have pushed it beyond what the availible fuel can handle. Here is a question that has helped me many times. Assuming 100% VE and a 300 CID 4 stroke engine, how much air is swept through the cylinders in 2 revolutions at idle with the throttlr closed? >It seems that unless you can factor in rpm (at the very least) in addition >to boost to more accurately predict knock, you have to *really* retard >ignition to cover the worst case, which makes you suffer a power loss most >of the time. That's why I figured the active J & S system would be much >better. Here you are nearly entirely correct. One other thing you are missing or forgetting though. Once pre-ignition has started, you have to retard the timing further to get rid of it than you would have if you prevented it in the first place. IMHO the best way to handle this is to figure out how much retard it requires to eliminate the ping then add a boost retard function to the ignition system so it retards the timing to that level under boost conditions. In other words retard the timing a couple of degrees at a time until the ping goes away then set your boost retard to that level. Adding a knock sensor from there will make sure that under abnormal operating conditions you won't have to worry about it. I mentioned once before in another post I had added a ignition retard device to one of my old Pontiacs. I finally have dug up the notes on it. This may be a "cheap" alternative for many. The unit I used was not and ECM. It is an ESC controller off a 82 Chevy P/U. This was a standalone system that worked with the normal dissy and uses a Knock sensor with a board to retard the timing until knock goes away. It is fairly easy to connect and doesn't require much besides the sensor and the proper ignition module. I forgot to bring the part #s home with me. If any are interested I can scan the skitz and include the part #s I used. I had to manufacture a dissy for my Pontiac as I was using a Tripower intake and a normal HEI won't fit behind it. You should be able to hook it into your current ignition system as the negative of the coil goes out to the module and as long as there is no "knock" signal it just comes back. Otherwise it "delays" it until the knock signal goes away. Scott ------------------------------ Date: Thu, 27 May 1999 00:49:50 -0400 From: Shannen Durphey Subject: Re: O/T Compression ratio and supercharging Thinking that higher piston speeds will tend to fill cylinders better on intake stroke, and lose less pressure to leakage on compression stroke. Shannen Gary Derian wrote: > > I don't see where stroke length has any effect but intake valve closing sure > does. > > Gary Derian > > > > Another tidbit that may or may not help is that my 91 Mitsu Eclipse > > > Turbo 5-speed had only 120 lbs. of compression pressure on all four > > > sylinders.... > > > > > I believe that cranking compression ratio has more relation to stroke > > length and valve timing than compression ratio. Anyone? > > Shannen ------------------------------ Date: Wed, 26 May 1999 22:18:56 -0700 From: garfield@xxx.com (Gar Willis) Subject: Re: 7730 and dis On Wed, 26 May 1999 22:44:45 -0400, "Bruce Plecan" wrote: >Would you share the part no., or application of that sensor?. >Does anyone know which, of that sytle sensor is the most compact?. Sure, once I unpack it. B) But it's just the vanilla GM mag crank sensor that's used on tonsOcars. Nuthin special. Gar ------------------------------ Date: Thu, 27 May 1999 00:19:02 -0500 From: "G. Scott Ponton" Subject: Re: 94 Truck problem solved Carl, Great to hear you found that one. Although I had no input for you I was thinking about it for the past few days. Sounds like I'm not the only one who forgets the "basics" from time to time. I will definitely remember what you found in the future. Scott ------------------------------ Date: Thu, 27 May 1999 00:29:05 -0500 From: "G. Scott Ponton" Subject: Re: O/T Compression ratio and supercharging Stoke length is the forgotten variable. It has a lot to do with cranking compression. The stroke determines when the intake valve closing event has the greatest impact. As the stroke changes the mean velosity of the piston changes. Also the piston and rods relationship to the crank changes as well as the dwell time at TDC and BDC. Scott ------------------------------ Date: Thu, 27 May 1999 00:16:29 -0600 From: "Programmer" Subject: Re: v8 block thread cleaning After hot-tanking and jet washing, all threads are re-tapped, blown clean and where needed, sealer is reapplied to bolt threads at "torque" up time. Hope this helps...if this is just at valve job time, to risk non-contamination, I'd just clean all bolts and apply sealer to the threads again. SnapOn does make a handy air powered vacuum cleaner !! Lyndon IPTECH - -----Original Message----- From: Stowe, Ted-SEA To: 'diy_efi@xxx.edu> Date: Monday, May 24, 1999 6:34 PM Subject: v8 block thread cleaning > >howdy. > >what do you guys use to clean up the block head bolt holes ? >it would be criminal to torque my shiny heads to all that crud down there, >which I think exits to the water jacket and or the oil pan ? especially with >the arp thread sealer/lube on them. > >I see that snap on has a thread chaser tool set, rtd-42, however I can't >seem to find a local snap on guy to buy it from. > >compressed air would blow that junk down into my engine beyond any doubt. > >so if you were doing a valve job, what do you use ? > >thanks, Ted Stowe > ------------------------------ Date: Thu, 27 May 1999 00:33:53 -0600 From: "Programmer" Subject: Re: Prowler V6 Todd, the only problem being the transaxle !! Lyndon IPTECH - -----Original Message----- From: Todd....!! To: diy_efi@xxx.edu> Date: Tuesday, May 25, 1999 11:36 AM Subject: Re: Prowler V6 >Cool to know! > >HOWEVER, accordin to my calculations at: >( http://www.c-com.net/~atc347/dragtable.htm ) > > >Mid 14's are not my idea of a quick car, ESPECIALLY for that price! > >Even a simple lil paxton or turbo would've probably DOUBLED the power, >thus givin it about 400 instead of a puny 200 hp at the rear wheels! >ALSO giving it a quarter time in the 11's! Beating out the VIPER by a >fair amount! > >What do ya think? > >LATER! > >Todd....!! > > >AL8001@xxx.com wrote: >> >> The 99 Prowler has the all aluminum 3.5L V6 also used in the LHS and 300M. >> The drive line of a Prowler consists of a front engine and a rear mounted >> trans axel. Similar to a Porsche 924/944, 928 and the 65 Tempest. >> >> 3.5L all aluminum DOHC V6 253 HP @xxx. It also has a >> dual tuned intake system to give a broad power curve. Compression is around >> 10 to 1. >> >> Sounds like enough for a 2,800 Lb street cruser to me. >> >> The 98 and older Prowler has a lesser 3.5L V6 cast iron block with a aluminum >> head. >> >> Power (SAE Net) 214 bhp (157 kW) @ 5850 rpm >> >> Torque (SAE Net) 221 lb ft (303 Nm) @ 3100 rpm >> >> Max Engine Speed 6464 rpm >> >> Harold > > > ------------------------------ Date: Wed, 26 May 1999 22:28:52 -0600 From: "Programmer" Subject: Re: Ignition advance, was Re: alternative engines, WARPED Bob, I'm sold--you going to post the technical on this setup sometime ?? Lyndon IPTECH - -----Original Message----- From: rr To: diy_efi@xxx.edu> Date: Wednesday, May 19, 1999 7:39 PM Subject: Re: Ignition advance, was Re: alternative engines, WARPED >Bruce (or is that Grumpy?) wrote: > >>Kinda depends on the WOT pressure drop across the carb., and spring rate of >>the vac, advance used. Even with the same no. degrees per amount of vac., >>by different spring rates/dia. combinations things could vary. Going from >>6-10 start to 20 something at 700rpm, 30 something at WOT (@3,000 rpm), and >>40ish at cruise with a OD kinda hard to do thata way (mechanical). Hence >>the real beauty of ecm's, IMHO. >> Grumpy > > >Bruce is speaking huge amounts of wisdom here, nothing can come close >to how an ecm handles spark control. > >I've installed a '747 ecm and spark control system on a carb'd car, >what a difference. Drivability, power, mileage, have all improved. >(Yes, I'm still working on the write-up. The cutoff is next week, >as I'm going back to school, along with working). > >Couple of things that mech/vac distrib's aren't/can't do: > > A 210 point table, based on rpm and manifold vac, that defines > the main spark advance value. This in itself blows away any > centrif/vac-adv distributor. > > Startup spark, additional timing added for a short time after > the engine is first started. Keeps engine from stalling (choke). > > Coolant compensation spark, additional timing added/subtracted > as a function of engine temp. > > Hi-way spark, after a set period of time, above a set speed, > additional timing added for better mileage. > > Knock detect and retard, along with testing of the ESC system. > > PE spark, at WOT, additional fuel is added, and spark is also > added to take full advantage. > >Well, more than a couple, but I hope I can get the idea across. >I'm sold on this... > >BobR. > >>>| I could be wrong at this, but what I have seen is, ported vacuum is >>>dead >>>| at idle, because it is above the butterfly....and as throttle is >>>increased, >>>| vacuum is generated at the "port" and does not go away at full >>>| throttle,,,,,great for emissions but terrible for performance,,,,,the same >>>| for MPG.... >>>| -Carl Summers > >>>>| You sure about that? I have always understood that a vac advance can >>>>| reads ported vacuum in order to affect a curve that begins as the >>>>throttle >>>>| is opened and increases as more throttle is applied, up to the point at >>>>| which all vacuum (manifold and therefore ported as well) fades under >>>>heavy >>>>| throttle openings, at which point the advance will decline again and the >>>>| engine will see only mechanical advance. This is apparently to provide >>>>| extra advance for economy at part throttle. Anybody who can further >>>>| illustrate this concept, please do because if I am wrong here I'm going >>>>to >>>>| have some serious rethinking to do! >>>>| Aaron Willis > > ------------------------------ End of DIY_EFI Digest V4 #311 ***************************** To subscribe to DIY_EFI-Digest, send the command: subscribe diy_efi-digest in the body of a message to "Majordomo@xxx. 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