33 Coupe Adjusting and Tweaking 12        5/16/09


Optimizing my setup

My car has been on the road now since January of 2006 and so far things have been going pretty good. I like cruising to car shows, taking friends for rides and of coarse, playing around on the freeway on-ramps. But one thing has been in the back of my mind this whole time... 'am I really getting everything from the motor that I should be'! What do I mean by that?  Well...let me try to explain.

I'm running 11:1 static compression on pump gas (91 octane hear in Ca.), I've had the timing backed off a little just to be on the safe side (so it don't have detonation). If the engine starts to detonate, it wouldn't take long before that would destroy some pistons. Now this was all something I had thought about when I was in the planning stages of building the motor years ago. And there were a couple of things that I've done to help this out, like using aluminum heads and a large overlap cam shaft. So far this has been working because I haven't experienced any problems. On the other hand, what is the optimum timing setting for my engine combination? If I were to change it by a few degrees, how do I know if I'm going in the right direction (because it's really hard to tell using the seat of your pants method)?

One of the other things I really didn't know about my engine was, how rich or lean the air/fuel mixture is with my carburetor at part throttle (freeway cruising) and wide open throttle (WOT). I've taken out a few sparkplugs over the years and examined them but it's really hard to tell, at least it is for me. I thought about buying an air/fuel mixture gage that reads your exhaust gases but that unit costs around three to four hundred bucks, depending on which one you buy.

So how do you find out all of this information? One way is to take your engine to a place that can dyno it for you. But that would require me to tear apart the whole front end of the car just to get the engine out, and I don't think I want to do that. But there is one other option out there, take the car to a place that has a chassis dyno.


Chassis Dyno

On April 24, 2009, I went to a place called Westech Performance Group in Mira Loma, Ca. Westech has both types of dynos, chassis and engine dynos. Their located about 45 miles from my house which makes it an easy drive. The only down side to this is... if something broke on the car while dyno testing, I'd have to get towed home. But I'm happy to say that I made it there and back on my own power and I had a great time while I was there and learned some stuff too.

Here is what the chassis dyno area looks like. One of the nice things about this type of chassis dyno is that I didn't have to drive the car up on some kind of elevated rack. Westech's is built into the ground so just about any kind of car can use it. Another nice feature is that rollers that the rear tires sit on is a two piece deal (split drive rollers). That's good news for people like me that have a low front-end which makes getting into position a piece of cake.

Notice the two big fans at either end of the car. These help keep the engine cool and remove exhaust gas's too. If you needed more help getting rid of the fumes, they have a dual suction unit along with some flexible tubing which gets vented through the roof too (large metal hose on either side of the car).



Taking a look around the shop you can see a few cars in various stages of work. The El Camino that you see below turns out to be 'nobodies' car and they use the back of it as a work bench and the motor as a test mule.

If you look close, you can see a large black tank right below the ZEX sign. This tank holds 2300 gallons of water that gets used for the engine dyno room, which is just to the left of the tank. Westech has two engine dyno rooms and they were testing someone's motor while I was there which was pretty cool to see. And it's much louder than you'd expect when your standing right next to the room watching.



See what I mean, this worked out to be a great place to store my hood and air cleaner while we were working on it. It's hard to see in this shot but on that left wall behind those cars are about 15 different engines that have all been dyno tested at one time or another. On the back side of that same wall is another bunch of engines that have seen their time doing some testing as well along with a Dodge NASCAR engine from last year.

Westech does dyno work for all the big magazines like Hot Rod, Chevy High Performance and many others. I've read about them many times and have been wanting to do this for awhile now. Well I must have mentioned them to my wife before because she bought me a test session for my birthday this year which is why I'm writing about this now.




Strapping the car down

Here you can see the split drive rollers (that I was talking about earlier) along with the car strapped down. Speaking of strapping the car down, notice the holes in the concrete with the chains coming out it them. There are many rows of these behind and in front of the dyno area that get covered with small metal caps when not in use. This makes it very easy to accommodate just about any vehicle that rolls into their shop. They used two sets of straps in the rear and in front just to make sure things don't move around, which was fine by me.

See that red air hose going to that strange looking triangular thing? That device gets plugged into the dyno's computer and reads the air/fuel mixture from the exhaust pipe. This is how they determine what jet size the carburetor needs along with other types of tuning.



This is Ernie that runs the chassis dyno area. He was a really nice guy and a very conscientious worker. If you look close, you can see a fender cover on my car but under that he put some nice soft white towels down first (which you can see at the front of the fender cover). He got bonus points for this in my book!!


Time for WOT

I drove in with the engine at 30 degrees of total timing and after the first of three dyno pulls, it was time to do some adjusting.

Here you can see Ernie re-jetting my carburetor because after the first dyno run, we found out it was running way to rich at cruising speeds. The carb started out with jet sizes of #78 for the front and back (which is stock for a 950HP Holley) but then he tried #76's in front and #81's in the rear, which made it run much better for cruising and worked good for WOT too.

The other thing he tried for pull number two was adjusting the timing from 30 degrees to 35 degrees but the engine made about the same amount of horsepower as the first pull.



For the third and final pull on the dyno, the timing was set at 32 degrees and one other thing they did to fine tune the carburetor was to use a different size of high speed air bleed. The ones that came in it stock were .032 but Ernie tried .036 and that made it work even better at WOT.


The Results

After the third pull, Ernie had a smile on his face and said that it liked the 32 degrees of timing because that made the best horsepower of all. How much did it make? It made 429 horsepower at 6300 RPM and 404 pound feet of torque at 5100 RPM.

This was the first time I've heard my car run and not being in it because I'm always the one driving it. Ernie was the one working the throttle on every run because it's their policy. And I'll have to say, it was a little weird seeing someone else working the controls while I stood and watched hoping nothing would go wrong...like the engine coming apart (damn that would suck) or some of the straps breaking. Funny what goes through the mind when you're in that position (it's a very helpless feeling).

For those of you that don't know about chassis dynos, all the horsepower and torque numbers are taken at the rear wheels which is the way this type of dyno works. And with this being the case, the numbers that you get are much lower than if they were taken at the flywheel, called 'brake horsepower' (like if the engine was out of the car). Why are the numbers lower? Because of what's called 'parasitic loss'. What's parasitic loss? It's basically friction, which causes power loss as it goes through the transmission, driveshaft and rear-end.

With my car having a nice strong overdrive transmission (4L80E) and a really stout nine inch Ford rear-end, that's all good news and it makes these two items hard to break. But the bad news is it doesn't help matters on the dyno because both of those items rob and eat up a lot of horsepower. On the other hand this is the cost of having reliability. How much does it eat up? That's the big dollar question! With my setup, you can expect about 25% loss through the drive train which would put my numbers into the mid five hundred range...I guess.

Now I told myself not to get wrapped up with the numbers before I did any testing because all I wanted was to optimize my setup. But it was hard not to get wrapped up in them and I ended up slightly disappointed at the end of the day. On the other hand, Ernie told me that those numbers were the best that he's seen for a street rod in the three years that he's worked there. I don't know if he was being nice or if that was really the deal but either way, my engine runs better now than it did before so I'm happy.


Dyno Video

I took a couple of short videos with my digital camera and then made this short movie (better than nothing) which you can see right here. The size of the video is about 13mb. and is in wmv. format and should play on just about anyone's system.

Once I was on the road back home, I smelled something weird and when I pulled into the garage, I looked underneath the car only to find an nasty oil leak. But where was it coming from?


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