420A 2.0 DOHC TUNING

[DSMTuner]

I have a 97 Eclipse RS. I have added an AEM Cold Air Intake, AEM Adjustable Cam Gear, Lightend Underdrive Pulley, CAT Back Exhaust, Magnacore Wires and NGK Iridium Plugs. Now my Question is how would I go about Tuning the AEM Adjustible CAM gears as far as Advancing or retarding them?

 

[evelrod]

Well, to start. BUY A BOOK ON CAMSHAFT TIMING AND SETUP. (Carrol Smith "Tune To Win" as an example) Find yourself a dyno with a friendly, patient, operator---or a drag strip where you can make THREE runs per camshaft timing change to take an average---

THEN-----start by altering your timing (single camshaft engines) by retarding 2 degrees at a time, I start getting nervous around 6 or so, so don't get carried away,you can break things. Valves hit pistons, valves hit each other etc., yes? Make notes and then do 2 at a time advanced, more notes----CAMPARE ----- pick the setting that suits you. Keep in mind that with EVERY timing change you MUST optomize ign timing and fuel settings if the computer doesn't do it for you.
DOHC engines get a bit more difficult, but with your car, sticking to the factory specs will probably yield best results overall. If you still wish to continue, make a graph of the timing specs for the intake and exhaust cams (have them 'profiled' ) Take the factory specs, if you can get them, and overlay them to what you have. By making small variations in timing , the graphs SHOULD point you in the direction you wish to direct your improvement(?) in performance. Ultimately, make small timing changes and be AWARE of interferance. Split overlap is a much overused term you will find in camshaft setup (works well enough as a referance point in single cam applications) with DOHC engines that the 'split' can be just about anywhere depending on where you set BOTH in and ex cams. Keep in mind that I have over 35 years experience in building and racing DOHC engines and I am STILL confused much of the time.

My apologies, DSMTuner. I will stop here as this post was intended to EASE your setup problems. This is a TERRIBLY complicated part of performance that there is just NO way to make it totally SIMPLE. All I can reccommend with certainty is to make VERY small changes, check for clearances, make a few test runs and change your settings the OPPOSITE direction. This SHOULD give you an idea which direction you need(???) to change your timing setup. Just do not get carried away and go too far. SMALL changes.

Perhaps Larry Meaux can add to this as I seem to be having a difficult time explaining what is to me both simple and complicated at the same time. In racing, camshaft specs and setup is STILL a VERY closely guarded SECRET!


Rod

 

[DSMTuner]

OK yes I have the DOHC in my engine. Can you tell me what a good setting is to start out at..... right now they are set at factory setting. Would I start by Advancing the Intake Cam and Retarding the Exhaust Cam or Vise Versa or what? Which would give me better HP and Torque? and A place down the road just got a dyno but it's 75 bucks for 3 runs, and well I'm not rich.... yet anyway hehehehe... .. . let me know THANX
kenny

 

[ludikris]

Kenny:

Unfortunately tuning isn't cheap but, my belief is that if you tune on the dyno, you'll get more consistant results than by taking the car down the strip. You would have to be quite consistant to recognize any gain from timing IMHO. I think that you could end up chasing your tail at the strip.

Usually, dynoshops can be rented by the hour, 1/2 day or day. With an experienced tuner, you should be able to dial them in within 3-5 pulls. As Evelrod pointed out, get a book or two on camshaft tuning, and/or do some searches on the DSM boards for similar settings to begin with.

To reduce the cost of the dyno, see if you can get a group dyno day organized with the owner. If you can get 5-10 cars in for a day of tuning, you can typically get a reduced rate after working with the owner. It's good (and free!) advertisement for the shop!

 

[evelrod]

Kenny, dyno time is obvioulsy the best way to set up an engine. Strip time is only my second choice for you as it worked for me(BROKE, with all caps was I) in the late 1950's. I made a 'zillion' runs setting up many different cars(a few ran at national level, including many records). I didn't 'see' s dyno until I moved to California in '66. It worked for me then and, with a little care, it probably still works. In your case, the factory has gone to great length to optomize you cam timing for general/high performance use. What you will gain by 'fiddling' with you existing cams is minimal. The exhaust cam may be a good place to start. With your other mods you may gain a bit---just don't expect great changes. Again the obvious is to check around and see if there are any articles or written material on your engine. It is a very popular car here in SoCal and local clubs are everywhere. Check carclubs on the net, you might get lucky. If I were you (that is what old guys say to young guys about to take on more than they can chew) I would find someone who has undertaken an engine modification plan on your engine. It will give you a starting point. Like I said, the little RS's are EVERYWHERE around here!!!

As I sit here I remember my first Lotus DOHC back in the '60's. I like where you are going with your car because it's what I did. I bought EVERY book on engines/race that was on the market. Bought ALL the service manuals from Lotus ($$$$$$$$$$$$$$$$) and read them all several times before making a 'plan'(?) --- then I just tore into the thing and started making changes. It worked on Chevys and Fords and it worked on exotic DOHC engines too. Just a LOT more -time-money-complication-blood-money-blood-money---I hope I make my point, eh?

I wish you luck with your 'adventure'. Just don't expect to get rich with all this new knowledge you will ge gaining (good or bad). Do try to 'scrape up' enough $ to rent the dyno, it will be cheaper in the long run!

Rod

 

[MaxRaceSoftware]

and A place down the road just got a dyno but it's 75 bucks for 3 runs, and well I'm not rich.... yet anyway hehehehe... .. . let me know THANX
kenny
==========================================

$ 75.00 dollars for 3 runs on chassis dyno is a pretty good deal ( $25.00 per) ...thats the same price for chassis dyno
around here .

with a DOHC engine , it should be easy to dial in the cam to what the engine wants and max-out it out for that cam's particular specs

but if its the original OEM cam, i don't think you going to see a bunch of power from where the factory put it .

Larry Meaux (meauxracing@mindspring.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers

http://www.mindspring.com/~meauxracing/

Support Israel - Genesis 12:3