Great Article on detonation/preignition
 

Grab a large coffee for this read. But I found it very interesting. Helps explain whats really going on inside a cylinder.

http://www.streetrodstuff.com/Articl...tion/index.php

Pretty interesting article. I like the "tin-ear" method; I have something on the dyno now, I think I will give it a try and see if the noises are any different.

Thanks for the info.

good info
 

I was thinking of leaning my wot (11.0:1 ) but it looks like i`m good and can even go a bit richer..









The Head porter I`ve used always preaches about the BBC combustion chamber design and how much improvement there`s to be had for more power, better more even burn, less detonation potential and better fuel economy.. while his results speak for themselves this confirms what hes been preachin

I know a lot of guys running boost on street and strip, tuning for mid 11's at wot . However , they are at wot for 10-12 seconds. I like wot for 10-12 MINUTES. Gm might have been on to something there

The chamber design is also one of the many reasons that the new generation LS engines perform so well, along with better overall head design and a number of other factors. Makes me wonder what the future holds for high performance.

Great article, BTW. How many folks are running knock sensors on their engines to tell them if they are detonating? Even without FI, it would seem like a helpful thing to have, even if simply wired to a large red idiot light on the dash to tell you to back off if any detonation is picked up.

You read my mind.. thats on the winter project list!

Wonder if something like this might work? http://www.viatrack.ca

Fuel also acts as a cushion in the cylinder just b4 the big bang..when i tune nos i pay no attention to the afr,,all i concerned about is the egt's..likes joes said its over with in 6.78 seconds but you can still destroy alot of chit in 4..

why would you not add afr guage to the tuning toolbox?

I'm curious about the talk of using the "tin cup" in the dyno room to listen for sounds of detonation. Why not just use a knock sensor? Also found it interesting that the article says detonation can trigger a drop in EGT's. Would one expect to see the EGT's elevate just prior to the detonation event?

I also found the discussion on preignition interesting. I wonder how many preignition events have been triggered by cross firing on spark plug wires, particularly on cylinders that fire successively with wires that run close together?

no doubt in my mind that can,and does happen,i remember a car i had years ago,if you opened the hood at night it looked like a fireworks show.todays wires are much better.

Hey Mike, was it kinda like this??


http://www.youtube.com/watch?v=CMNry4PE93Y

Fixx
 

Mike

Why,,only guys that don't know how to read a spark plug has no right tuning a engine..a afr gauge wont tell you timing tracks and besides what happens in a cylinder and where all the exhaust ports meet to where the afr gauge is don't tell you what EACH and individual cylinder is doing..its a combined reading between all the cylinders and dont tell you if one it a few points rich and another could be a few points lein.a egt probe rite at the exhaust port and spark plugs do..

Used to check for bad wires that way . In the dark, a bottle of windex, spray wires down, and watch for the spark show .

to each his own,with all the good afr gages out their today it would be foolish not to put it in the tuning toolbox,but if reading plugs and egt,s is how you do it,carry on.imo,afr gage is the most important tool for proper tuning.

yes,that,s it dan,LOL.

Theres no way you can read a plug and tell me if its 11.7 or 11.2 , I`ll agree reading individual plugs gives you a better idea when the AFR gauge gives you an average .
I Go Pro my runs to check afrs.. no need to stop 20 times to check plugs, plus it takes a while before the plug gets some color so on 2 motors that could take all weekend.. AFR takes 10 minutes.

I like turtles

I agree. The AFR gauge helps get you in the ball park for sure, but obviously isn't the end all to the tune. Problem with EGT gauges is they aren't practical in a boat. How does one install 16 probes in a twin engine boat and monitor them, along with 18 other gauges while out on a poker run in 4 ft'ers?

This is where things get fuzzy in my opinion regarding timing. For example, the EGT gauges on a dyno pull, might show lower temperatures with added ignition lead. However, the dyno pull is just that, a dyno pull. Nothing is heat soaked, nothing really has the time to stabilize. For example, on the dyno you might get the EGT's to 1300*. But, now, you stick the engine in the boat, and hold it WOT for for a couple minutes. You'll find the EGT's raise to a alarming point. This is probably where the tuner/builder/ has to determine from his own experience, what to give the engine for timing. Just because it didn't detonate on the dyno, there has to be a little cushion there for slightly lesser quality fuel, hot ambient air temp's, different loads, etc. The same engine going into a 30FT stepped bottom, might tolerate more timing than the engine going into a 41 apache. Its almost like a diesel. You can install a tuner, and power adders, and be totally fine punching it from 0-80mph, and EGT's look great. Now, strap a 10k lb trailer on it, and go up a long hill. Without detuning it, or backing out of the throttle, you'll surely melt it down.

I try to look at things Mercury did. While their engines may not have produced the maximum power, maybe not the best parts, one things for sure, they weren't known to melt down. Most stock untouched mercury setups, can withstand an extended amount of WOT run time, and do it weekend after weekend. They ran them Fat, and were conservative on timing, and compression. You know how much ignition lead a 800SC engine had? 28* total. a 600SC had 33*, and the 525SC had 35*. Some guys will say 28 degrees will melt the exhaust valves, and 35* will detonate in one pass. They weren't guessing at mercury on these tuneups, they couldn't afford too. Point is, every setup is different, and sometimes you just cant have it all. lots of timing, leaner air fuel ratio's, lots of boost, hot spark plugs, etc. Otherwise, your "marine endurance" engine, is no different than the engine the guy is running in his strip car. You have to be willing to give up a little, to gain longevity. Did mercury ever build a 10.5:1 aluminum headed N/A engine? Nope. So the guy who says "I can run 10.5:1 in my 502 build with 38* timing and make 100HP more than a 525", probably can. However, the question is for how long. I'd have no qualms about holding a stock 525EFI wide open on marina gas all day.

As far as AFR readings, I'd like to know what mercury supercharged engines had for AFR' readings? Like a 600SC, 800sc 575sci, 1075 etc. My guess is they aren't anywhere near mid-upper 11's at wot. I would bet they are in the 10's, probably low 10's at wot.

With that being said, Im ordering smaller blower pulleys. :daz:

Good post, MT, and I agree that you have to be smart about tuning these engines. The discussion in the article about combustion chamber design and timing greatly interested me. I am switching from stock GM heads to AFR 265's on my little old 489, and I am wondering how much that will affect the timing curve for the engine. Not sure if the AFR chambers are a true "fast burn" design, but they have to be more efficient than the 50-year old technology that the GM heads were sporting.

My plans for this engine are to end up in the 575 - 580 HP range with a conservative tune to help promote longevity. I like turtles too :D - don't want to be the hare blowing up out on the water.

Food for thought. Stock Supercharged Cobra Mustangs fuel down to 11.1-11.2 at power enrichment. Turbo Buick guys, are fueling into the 10's on afr. A buddy of mine with a boosted up Grand National, actually made more power on the chassis dyno at the richer AFR. Leaning it down lost some power.

I personally think on a boosted marine engine, tuning to upper 11's, at full kill, is gonna cause an early death. I personally pulled some fuel from my setup this year, thinking I was giving up power in the 10's on afr. By leaning it out some, the boat actually slowed down. Maybe on the dyno it works for making max hp, but maybe for me, the added fuel helped cool things down. IDK.

Say it MILD THUNDER....say, i like turtles with small blower pulleys!!!!!!!

265's are too small for a 489,,i would step up to the 295's...you will hit a wall @ 5k with the lower cfm number..

Glad

Off topic but...., that is 100% incorrect, and bad advice.

enlighten me!!!! EDIT.. did not want to hand out the popcorn on this one..

afr,s website sais the 265 is for 396 to 468 cu in,i know we are talking about 21 cu in difference but if it was my decision id go with the 290s,just my opinion.

"enlighten me!!!! been their done this would not rev over 5 k,,maybe good for a cruiser..switched to 295's and picked up 1200 rpm.. "

:popcorn:

Here we go! ;)

I'm going by what was recommended to me by a highly regarded marine valvetrain designer who ground the cam I am running. Have read several articles that says that these heads can support 700 HP - not saying a 489 would ever make that, but just what I have read. I never plan to spin this rig above 5500 RPM, so I guess that is a factor. Sounds like your results varied.

Oh $hit. How does every thread get into a pi$$ing match! Just wanted to share an article that I found informative.

Im going back to playing with my Turtles. :food-smiley-007::gfight:

How ?? leave it up to someone from the upper NW Bc to throw out his comments,,it even reads up to 468 cid on afr's website..

I got your popcorn rite here...........ok your pro engine builder knows best and its your money so spend it how you like...ill see you on your next trend......

Oh geesh, sorry, didn't want to start a sh!+ storm - things always get twisted around on the web, that's why I put the smiley on my post! Like I said, I'm just going by what the cam grinder suggested for my application, someone else might have different requirements. My original post was discussing chamber design and timing requirements in regards to the article that MT posted anyways. I never intended to drag this into a discussion on port volume / CID requirements. :offtopic:

MT, sorry for the :hijack: - it was never my intention.

If you did nothing but change a set of AFR 265's to AFR 290's and picked up 1200rpm, then you had a serious set up issue, most likely valve train related, and cost the customer a lot of money by changing out heads rather then fixxing the original problem. I have run AFR 265's on everything from 489's to 557's. I know exactly what they are capable of and have several 509's turning 6000+ rpm and making 600+ hp.

Did not mean to start a pissing contest but your post was ridiculous. Mike stated his opinion, which is great, it's an opinion that can be discussed. You on the other hand made a statement like it's a fact "265's are too small for a 489,,i would step up to the 295's...you will hit a wall @ 5k with the lower cfm number.." For starters it's CC's not cfm, and how do you know what his budget is, how many rpm he wants to turn, how much power he's looking for, etc. There are way too many variables for a blanket statement like yours. As far as backing up your statement by referencing a baseline recommendation f'or an automotive engine from AFR;s website... Give Tony Mamo a call and tell him your building a sub 6000rpm 489 for a boat with low compression and want a broad flat torque curve and want to do it on a budget. If he doesn't think the 265 is an excellent match for that application I'll fly down there and kiss your azz. Also, if you're not tuning your NOS system with wide band O2's, then you're leaving a lot on the table..

Sorry for the hijack MT

Budman, yes, you will likely need less total timing with the 265's then you would with the old iron heads.

i guess i should say why i would have went with the 290 instead of the 265.i like the idea of a cnc intake&exhaust port as the repeatability with the cnc machines is exact.if the build was on a tighter budget,i would not hesitate to use the 265s.in my opinion the hp&torque figures would not be very different with either of these heads.i also believe the 290s will make more power if useing a cam with more lift&duration and will be run to a higher rpm.

First What ever..you only post to stir up chit with EVERYBODY.....OR just to make money off someone..you never post just to lend a helping hand period..their has to be a money involved...

I really dont give a rats ass what he does with his engine,,could put some 300 hp peanut port heads on their for all i care now..and the 290's are a way better cylinder head then the 265's ....i like to leave room in a engine for future builds unlike you who would rather sell someone another set of heads instead of using what you got on another engine..

as for afr's on the race car yes their are afr sensors on each cylinder,,its part of the race pack system thats on the car....yes i use them,i also read the charts after the runs but the egts give me a base line..

so your saying a 265 (out of the box) is making 600 hp on a 509....rite!! prove it....

I don't know, I think correcting misinformation posted by wannabe engine builder / tuner's like you is definitely a help to anyone who doesn't take your bad advice.

I'll let you argue with yourself on that one..

Here's a dyno sheet I posted here a couple years ago, I can dig up some more examples for you later if you need. This particular sheet is on 89 octane with Imco manifolds, running the raw water pump and power steering pump, stock 502 mag bottom end, rmbuilder cam and valve train. With headers it made about 20hp more and 10 lbs/ft less

How would those heads compare say to like the 305 Rectangle AFR on a similar build? Say same 502ci, same rpm band?

Why must Mild Blunder always cause trouble with his threads!?!?!?

Turtles never get offended , they got thick skin, its like a shell!

This thread is like watching turtles bang. http://www.youtube.com/watch?v=4pyorz7iIwA