Landracing Forum
Tech Information => Technical Discussion => Topic started by: GH on February 12, 2009, 08:20:45 AM
-
What do some of you guys do with ignition retard when the engine is under boost? I have a big block Chevrolet, turbocharged and EFI. We have been starting with 36 degrees and retarding to 26 degrees. This is at 15 psi boost, seems to work good but we are going to play around with it this winter on the chassis dyno. We have been using the MSD-6BTM but no we are going to control the ignition with the Megasquirt.
-
Are you loggin EGT?
-
I use one of those cheap EGT units with the 9V battery, the battery went south last August. It reads on the left bank only.
-
Gary, JMO but when you have a large displacement engine that's supercharged on the salt I don't advance the timing. I have enough trouble getting hooked up so I don't need/want the power down low. I run most of my stuff with very little if any timing curve. I know Scott will disagree but that's how I do it. Total timing on my turbo engines is all I run except some of the smaller engines < 300". Then I hove found it advantages to advance the timing to help the car accelerate off the push truck.
Now if you're going to ramp the boost with the M/S there might be some advantage to adding timing under lower boost levels but I doubt it. But that's why we have these tools, to try our ideas.
Good Luck this year.
-
Small engines with big boost can make for radical changes in horsepower when the boost comes in. Ignition retard is a good way of overcoming that. Gee, I thought we were the only ones that figured that out. Right.
-
Are you wanting to retard the Ignition for reduced risk of Detonation if so have you thought of water injection i thought about it for a nitrous set up and it may be worthwhile looking into,also gives you a nice cool charge,
I could be barking up the wrong tree but its a thought.
Oz
This was one of the answers i got it is in the Water/Methanol section
Well getting back to the original topic, water or alki injection does make wonders for detonation suppresion, cooling and octane boosting on forced induction engines. Now water/alki and nitrous hasnt been as widely researched and the people that have arent talking about it, i've talked to Rodney from Alcohol Injections Systems about it and this is part of what he answered me:
"Hi Rudy,
First of all let me say, running water methanol injection with nitrous is perfectly fine. We actually sell many systems to strictly nitrous users as it offers the benefit of increased octane while stabilizing the combustion process. This allows users to then run much less ignition retard while adding some extra safety to the motor at the same time."
The cons i see with running this kind of set up in N/A nitroused engine & water/alki injection would be tunning as it would run very rich since these systems are normally setted up for boost not nitrous and would need extensive tunning and scanning logging tools to get the proper A/F ratio when on the gas.
Try checking out all the alcohol/water injection at the following link: http://www.alcoholinjectionsystems.com/Tech-Articles/t7/articles.html
Rudy.
Logged
-
Mike, I drive off from the start line, so I think I need the advanced timing. I took your advise last year and short shifted as soon as the rear tires came loose. Was able to run 100% throttle for 35 seconds in 5 gear about 2 miles.
-
If I understand the rules correctly, the instant you use anything but water from a sealed container, you switch over to Fuel engine classes, and then you should probably just switch completely to methanol.
IIRC, there are two reasons you retard timing under boost in a gas engine. One is to supress detonation, but the other is that boosted air/fuel mixture burns quicker, so peak HP will occur with less timing under boost than it will NA.
-
Small engines with big boost can make for radical changes in horsepower when the boost comes in. Ignition retard is a good way of overcoming that. Gee, I thought we were the only ones that figured that out. Right.
I welded the advance weights shut on a bike I turbocharged decades ago so it had fixed timing (points/coil). The boost came on all at once with a vengence.
-
If I understand the rules correctly, the instant you use anything but water from a sealed container, you switch over to Fuel engine classes, and then you should probably just switch completely to methanol......
That is correct, but if you want to use water it is not a big deal. You just go to the fuel truck with your water container for the water injection in the car empty. Produce some bottled water. They will ask you to drink some and it you can still walk a straight line you pour it in and they seal it. Same if you are lucky enough to go to impound.
If you can make more than a run with your sealed gas tank on the car it would be a good idea to make sure you hold enough water in its sealed container so that you don't have to go back and get in line and add more and have it sealed.
If you are running fuel anyway then put whatever you want in the water.
We run Snow Performance water injection,
Sum
-
-when you are running a distributor---and electronically retard the ignition timing and/or use any other external timing trigger such as a crank trigger----you need to understand "rotor index".
-"rotor index" is simply the alignment of the rotor tip to the inner distributor cap terminals----and that alignment moved about with vacuum advance----- and with externally controlled timing triggers
-locking the distributor's mechanical advance can also affect this sometimes depending on how that gets locked out.
-It's very easy to have the rotor index alignment to the inner cap terminals move so far that the rotor is nearly 1/2 way over toward one of the next two adjacent terminals---and this is NOT GOOD.
-best way to verify what you have is to either get a clear cap to use for testing purposes----or cut a section out of a distributor cap to use for a test cap----cut this window about 1-1/2" long and maybe 3/4" wide----to where you can see well inside the distributor.
-then you can connect a timing light to the terminal nearest that window----see what you currently have for rotor index----and then watch what happens when you activate the boost retard switch.
-this all can be somewhat of a problem to understand how to fix----unless you have access to a distributor machine where you can install all your ignition components and test.
-if you've never been in there looking at rotor index it's well worth looking into.
-
If I understand the rules correctly, the instant you use anything but water from a sealed container, you switch over to Fuel engine classes, and then you should probably just switch completely to methanol......
That is correct, but if you want to use water it is not a big deal. You just go to the fuel truck with your water container for the water injection in the car empty. Produce some bottled water. They will ask you to drink some and it you can still walk a straight line you pour it in and they seal it. Same if you are lucky enough to go to impound.
If you can make more than a run with your sealed gas tank on the car it would be a good idea to make sure you hold enough water in its sealed container so that you don't have to go back and get in line and add more and have it sealed.
If you are running fuel anyway then put whatever you want in the water.
We run Snow Performance water injection,
Sum
I run the Snow system also to try and save the turbine. A diesel doesn't detonate, but high EGT's will damage the turbocharger turbine wheel. At $2500 a pop (not rebuildable) water is cheap insurance. Unlike the advertising brochures say, we did not gain 1 rwhp with water. But it did lower EGT's from 1800°F to 1650°F.
At Bonneville, they sealed our water tank, but at El Mirage they didn't.
-
What do some of you guys do with ignition retard when the engine is under boost? I have a big block Chevrolet, turbocharged and EFI. We have been starting with 36 degrees and retarding to 26 degrees. This is at 15 psi boost, seems to work good but we are going to play around with it this winter on the chassis dyno. We have been using the MSD-6BTM but no we are going to control the ignition with the Megasquirt.
Gary you need to double your boost :-D
JL222
-
John, I sent the turbos off and had them modified, just got it started yesterday. They clipped the impeller on the turbine side for less exhaust restriction and changed the compressor impeller and housing for more boost.
-
With our d blown engine we spent most of our dyno time on figuring a timing curve . We run a MSD 7al-2 with the boost retard for our application we started out safe and started adding timing until we made a number we were happy with. We also ran a water injection kit from the Supercharger Store wile running ERC gasoline , the water ended up costing us considerable H.P. We even tried turning the water injection on at different boost settings but it cost us power every time. It may be a good thing on pump gas or at higher timing but I was afraid to put in too much timing at 19 LBS of boost.
-
With our d blown engine we spent most of our dyno time on figuring a timing curve . We run a MSD 7al-2 with the boost retard for our application we started out safe and started adding timing until we made a number we were happy with. We also ran a water injection kit from the Supercharger Store wile running ERC gasoline , the water ended up costing us considerable H.P. We even tried turning the water injection on at different boost settings but it cost us power every time. It may be a good thing on pump gas or at higher timing but I was afraid to put in too much timing at 19 LBS of boost.
Did you try leaning the motor with water injection? My next computer will be able to post pictures. there's a chart from Ricardo's book showing water injection. He started lean on fuel increased boost to detonation then added fuel and boost on up to no more power could be made with increased fuel then added water injection and increased power a bunch to limit of dyno but he also leaned the motor back to were he started.
JL222
-
Here's my guess (and only a guess):
Water creates thinner air, so when the water sprays, you need to advance the timing to compensate for the lower effective oxygen density.
I personally can't advance my timing due to something called bursting, but that's a different subject.
-
Honestly we did not have enough time to give the water injection enough attention. This was a big learning curve for me my crew (good friend and brother) and the dyno operator. Non of us had messed with a blow through carb set up, I just spent a lot of money on the blower, carb, engine etc. to get greedy on the dyno three weeks before speed week. We spent two days on the dyno and found 300 hp from start to finish with a very safe tune up and did not hurt anything we were far from leaning the engine out, overall I was very happy. I would be interested to see those sheets ,no one I know runs water injection and I would like to give it more attention on the dyno now that we have a good base tune up and timing curve. thanks Mark
-
Well, we did the dyno session last weekend and it went good. We achieved our goals, which were to carry power all the way to redline - the old turbo setup was too restrictive on the exhaust and started causing too much backpressure, and power loss, above 5900rpm or so.
Dynoroom, what we did with the megasquirt was the exact same way we were running his MSD ignition. We have the engine running 36 degrees advance, even at light load, and at idle. Then as boost comes on, we ramp downwards to a total timing of 24 degrees, where it seemed happiest on the dyno. (power increase was falling off with additional timing). Really, the *only* benefit we got from controllng timing with the megasquirt was the fact that we can (1) datalog our advance, (2) have better mapping based on boost if we need to "turn it up" on the salt (the 6BTM is a bit of a guess when doing this), and (3) best benefit of all was to be able to control timing during cranking. When the engine was warm, it would kick back on the starter when running 36 degrees on the MSD 6BTM setup. Now we are able to run a 10-15 degree advance when cranking, and it doesn't kick back on us at idle.
I'm not really treating this one like a street engine, with lots of advance under decel, etc. So basically I'm running it just like you would suggest. I know better than to disagree with you :-D and besides, who worries about the deceleration tune on the salt flats??
To the guy who suggested correct rotor phasing. This is great advice that a lot of people miss. We made sure that the rotor was directly underneath the correct spark tower when the engine is at it's peak power timing, or 24 degrees BTDC. That way, at peak spark energy demand, we have the shortest possible gap for the spark to cross between the rotor and the cap/tower. Thanks for the good advice!
Some other interesting stuff we found. Corrosion - BAD - underneath the injector clips. We had one cylinder misfiring on the first pull and as we poked around, we caught the corrosion... cleaned them all up, and she was hitting on all 8 just like always.
This d*mn salt is something else, unbelievable corrosion in such a short amount of time. It makes midwest winter roadsalt seem like Florida.
Thanks guys,
-Scott
I will post up a video soon.
-
Good post Scott with good solid information too. I'll be watching Gary's car this speedweek to see how it performs.
Good Luck to you guys.
Scott will you be at Speedweek?
-
Good post Scott with good solid information too. I'll be watching Gary's car this speedweek to see how it performs.
Good Luck to you guys.
Scott will you be at Speedweek?
I am going to try. The planets seem to be lining up that way... I *really* want to be there if Gary gets his red hat. We've worked so hard for it. It's been a LOT of fun and a huge learning experience... and we still need to meet in person,
-scott
-
Scott, I will not forget yours and Pauls help on getting me going year before last,
THANKS again Sparky
-
Sparky! I'm in Mammoth, Az. and I need to find someone who does louvers...you know of anybody or shop with a louver press??? (differant sizes will be needed) Either in the Tucson or Phoenix area. Thanks! Crow
-
Crow,
I have had louvers done for my Roadster by Gary Criss in Tucson. His number is 520.465.0726. I was very pleased with his workmanship.
Francis
-
:-D :-D :-D :-D Goldleaf! Tanks!!!! Just started the 39 Chevy p/u project and neede that info for the budget.... Thanks again! Crow