enkeivette

Anticipating detonation/ tuning problems with the supercharger going in I want a way to measure A/F and detect knock/ detonation (same thing right?). I'm worried that with my loud exhaust system I won't be able to hear what's going on in the engine.

I was looking at the LM1 but reading up on it, it doesn't seem to have any feature to detect detonation. Who makes an affordable detonation detection system?

Also, can I tune my engine with a simple guage from Autometer that connects to a narrow band O2 sensor?

bb69

I think you may be confusing the relationship between air/fuel ratio and detonation. A/F ratio will have an effect on detonation, but you can't detect detonation simply using an O2 sensor. The only way to detect detonation is to use a knock sensor. There are a lot of theories about knock sensors, but I would say most people agree that a knock sensor from a production engine with the same bore and stroke as your engine will work OK. The problem is you need to be able to read the signal from the sensor and determine what it means. The only people I know of making a system to detect knock are the guys at Megasquirt. The latest level Megasquirt can detect knock, and then retard the timing. That is a complete engine management computer though.

You can tune your engine to 14.7 A/F ratio using a narrowband. That should be OK for most parts of the map, but it probably won't be the best for idle, and certainly won't be the best for WOT. You really need a wideband to get a good tune. If your plan is to tune the car once and enjoy it, I would suggest finding someone with a chassis dyno and taking your car there. Most chassis dynos have a wideband sensor they can attach to your car. Detonation can also be spotted on the dyno plots as dips in power. A good tuner will be able to see that.

If you want to continue to tune the car yourself, buy a wideband system that has datalogging capability. Careful examination of datalogs can also find detonation as spikes in the A/F ratio. This is more complicated because it is related to the sampling rate, placement of sensor, etc.

Hope that helps.

Ken

PS. Spend some time reading through the tuning section of the Megasquirt forum. There is a lot of good information there that relates to all FI systems. http://www.msefi.com/viewforum.php?f...39b6e00df6d7b1

Matt Gruber

MSD knock alert #8964 $185

S489

can that unit be used for hyd roller lifters?

norvalwilhelm

No to the narrow band. It is just a switch to tell you which side of 14.7 you are on. I have both the wide band and the narrow band and the narrow band is a waste of $100.
It is the wide band or nothing.
With a supercharger under load you want about 11-1 ratio to keep you out of detonation and yet under light cruising loads you can be 15 or 16 to 1 without a problem.
Spend the money on the LM-1.
By tuning with it I doubled my gas mileage.

Maymyvetteliveforevr

Norval, which LM-1 do you have for your 75?

Matt Gruber

with the data recording of the lm-1 and the cheap price it has really obsoleted the narrowband. It takes a skilled mechanic to tune with the narrowband; few here have demonstrated the necessary skill, even with my tips, so no, i doubt u can master the narrowband, and with the LM1 low price why bother?

69427

You can do a reasonably priced knock monitoring system using a production sensor and knock module off a mid 80's 350 or a 4.3L V6. (I can get you the part numbers if you are interested.) You might even be able to find these parts dirt cheap at a junk yard. If you or a buddy can build a simple pulse stretcher/LED driver circuit to attach to the module output, it will give you a visual reading of when knock is occuring. Works great (I have one on my turbo 355) and is a nice inexpensive tuning tool.

olescarb

we use the NOx reading from a 5-gas exhaust gas analyzer as a precurser to detonation. the NOx level in the exhaust will rise as you get closer to detonation.

Knock sensor technology can read chassis noise or a engine noise such as solid lifters as knock, but take a look at this link http://www.jandssafeguard.com/monitors.html
I have not used it but it may be a good knock sensor system to look at.

also if you are using a carb on the supercharger be sure you use a carb with a boost referenced power valve.

i hope this helps

tshort

Here are some other ideas:
http://forums.corvetteforum.com/show....php?t=1368192

http://www.turboxs.com/more_info.php?ID=212

Personally I run the MSD Knock sensor unit. I didn't trust my electronics building capabilities and I couldn't afford the Knocklite.

enkeivette

BB69, I have never confused air to fuel ratio with detonation, sorry to give you that impression. Thank you for the info on wideband vs. narrowband, didn't know that.

Matt Gruber, I saw that unit last night. As my Summit order approaches $600 to complete my supercharger install (and I haven't bought a fuel pump/ regulator or retard box yet) I'm trying to be cheap. Maybe $185 is a fair price to pay though.

Norval, thanks for the encouragement. Is there any particular model that you recommend or is the basic one ok to use?

69427!, I am very interested! My dad is an electrician and I'm sure that he could build a pulse strecher/ driver circuit. If you have any part numbers that would be great, and if you have any more info on the pulse strecher/ driver circuit that would also be great. Any info you have, you've sparked my interest.

Olescarb, that guage would be so cool if I didn't have to buy the safeguard box to work with it. From the description I'm almost positive that the safeguard box is only made to work with FI cars. Also, since I'm using a centrifugal supercharger as opposed to a roots type, I will not have to boost reference my PV.

Tshort, TT always has some ingenious ideas. I will certainly read up on that. Thanks.

bb69

Sorry, I misread your post. The way I read it, I thought you were saying you could detect detonation by measuring the A/F ratio.

Good luck.
Ken

enkeivette

BB69, I see how you read it... I meant that knock and detonation were the same thing, not A/F and knock. Sorry that was confusing.

Also, I have had my car dyno 'tuned' before, 20 mins on the dyno if that. What a waste of $180. They told me that the engine was dangerously lean and did two dyno runs anyway. They told me that they would need at least another $180 to even crack open the carb. They didn't touch the timing. They basically found $2500 worth of work for themselves to do, at which point I realized that they were crooks. Don't worry I didn't give them anymore more than $180.

I paid $180 for a dyno run, not a dyno tune. Must have been a bad shop. I took it to Superior Automotive, stay away from those guys! Be warned! I've now heard several bad stories involving these guys from fellow hot rodders.

If I could spend a couple hundred dollars somewhere and have everything dialed in, with real tuning time on the dyno, I would do it. But after being screwed I realize that if you want it done right, you have to do it yourself.

bb69

Finding a good dyno tuner is like any other service; it is hit or miss. One of my buddies is a professional tuner so I had an "in". I still had to rent a dyno, but I ended up paying $200 for a couple hours on the dyno. The correct process takes some time. It will take more time with a carb, because you have to make pyhsical changes. With FI, you simply change some numbers on the screen. Anyway, learning to tune is fun in my experience. You will spend a lot of money on gas, but you will have a grin on your face while you do it.

If you are interested in finding a good dyno shop, let me know where you are located. My buddy does teaching classes all over the country and can probably tell you where there is a good shop.

Have fun.
Ken

enkeivette

Southern CA, Orange County. Thanks, I appreciate it.

69427

I'll dig up the info this week. I'm tied up with family visiting at the moment, but I'll get you the part numbers. The pulse stretcher requires a minor knowledge of ICs and transistors usage, so hopefully that won't be a problem. The pulse stretcher circuit drives a large LED for visual indications of knock, while it also increases the pulsewidth time so that it is easier to monitor the LED. (I mounted the LED on the rear view mirror of my '84 so I can see it out of the corner of my eye while driving.)

Matt Gruber

i'd like to see the pulse stretcher too.
but,
w/temporary quieter mufflers u can tune it while u drive, then take them off. will be real close a/f wise and ping perfect.

enkeivette

Why quiet mufflers?