Vortech Supercharged 4.6L Mustang GT
Part II - the 1997 season
By: Ed Olin (EDO)

During the winter after the 1996 season was over, a compression check was performed on the engine. It showed that 3 cylinders (cylinders 2, 3 and 4) had significantly lower than normal compression. That seemed odd since the car ran great and had no out-of-the-ordinary noises. Upon disassembly, it was noted that the pistons in those three cylinders had broken second ring lands (the area of the piston between the top ring and second ring). This kind of breakage is usually the result of abnormally high force (probably from detonation) pushing down on the top ring. The bores looked amazingly good and would be fine for a rebuild with just a very light honing, as there were no major scratches. The rest of the engine looked fine. In fact, the other 5 pistons looked like they were out of an engine that had been started once and run for a few thousand miles on the highway. With the exception of those 3 pistons, the engine really seemed to take all the abuse from the season’s 99 dragstrip passes (sometimes with severe detonation) very well.  

For the new 1997 season some changes were needed due to track safety requirements for cars running quicker than 11.99 seconds, while others were made to enhance performance or durability.

Modifications for the start of 1997:

1. Rollbar - A 6 point mild steel rollbar was purchased from Chris Alston’s Chassisworks. Even though it was specifically made for a Mustang, we decided to bend the main hoop a little for an even tighter fit to the interior side trim. I have to specifically thank Nathan Sten at this point since he did the complete fitting of the chassis plates to the various contours of the floorpan and notched all of the tube ends for welding. I would also strongly suggest that for anyone doing work with tubing, invest in a tubing notcher, as it is a tremendous time saver. The fit of the rollbar turned out excellent.

2. Safety bellhousing - This is not a direct bolt-on for the 4.6L in a Mustang and is covered in another article here on the CORRAL. Other than the safety bellhousing, a Heavy Duty T-5 (SVO part number M- 7003-Z) was installed, as it should be strong enough for this application. I’d be giving up the seemingly more desirable T-45 trans 3.37 1st gear ratio for the HD T-5 trans 2.95 1st gear, so a quick check was made using the Performance Trends’ Performance Analyzer program. It showed that the car shouldn’t be any worse off with the lower numerical first gear since the street tires were traction limited in 1st gear with the 3.37 gear. Based on this information and a limited budget, I kept the stock 3.27 rear axle assembly in place for this year too.

Link to bellhousing article:  http://www.corral.net/modular/bell1.htm

3. Subframe connectors - Somehow I managed to go all of last season without doing any damage to the car without these installed. I guess this says a lot for the chassis stiffening improvements that went into the SN95 Mustangs (94 and newer) that were not in the earlier FOX Mustangs (79 - 93). But since the welder was available for the rollbar installation, it now seemed like a good time to install some. I chose the best I could find - the SVO Heavy Duty Subframe Connectors (SVO part number M-5478-J), which along with being welded to the car also incorporate a cross brace on each side that bolts to the floorpan using the seat track bolts.  

4. Engine computer - Last year I ran with the stock EEC-V computer (and calibration) in the car and had reached its limits. Since I had to get something new, either a chip or a new engine control system, I went for the complete control system. A chip would have been fine if one for my particular combination had been available and I was not planning on any more changes, but neither of those applied here. I settled on the SVO EPEC (SVO part number M-12650-C81) as I knew other people having good luck with it in their 5.0L Mustangs and it would give me more control over the engine with various future parts changes. Just in case you are wondering, EPEC stands for Extreme Performance Engine Controller and can be used in two different ways. One way is "Piggyback" to the stock EEC so it only controls the engine under certain conditions (like above some user programmable rpm) and the stock EEC controls it at all other times. The other way is  "standalone" so that the stock EEC is not used at all and the EPEC is always in control. No wiring harness was available to adapt the EPEC to a 4.6L engine/vehicle harness, so it was much easier for me to fabricate a harness to use it in "standalone" mode so it would only have to connect to the engine and not interact with the rest of the vehicle. The EPEC is a very generic engine controller and can be used on any engine up to 8 cylinders, so it is well suited to anybody looking at engine swaps or major engine upgrades.

For a fuel and spark calibration starting point I just used the 1994-95 GT calibration that came with the EPEC with a few changes. I set up the wide open throttle (WOT) Air/Fuel ratio (A/F) a little richer at higher rpm due to the supercharger and not wanting to get into detonation. It went from about 13.5:1 at low rpm and progressively went richer to 11:1 at 6000 rpm. The spark was just retarded about 2 degrees above 5000 rpm from the 1994 GT calibration to be safe from detonation. The rev limiter was raised to 6400 rpm, since last year’s stock 6000 rpm limit just didn’t seem to be high enough.

5. Bigger air meter - Deciding to test the bigger-is-better theory, I opted for the biggest of them all, the Pro-M 107 mm air meter. As you can see in the pictures, it is BIG. It would appear to be overkill, but I needed to change to a different air meter anyway, since the stock 80 mm unit was no longer capable of measuring the high airflow the supercharger was pulling through it. Actually, the people at Pro-M could have recalibrated the stock air meter for a higher flowrate, but their big air meter was just to enticing. The 107 mm air meter and the big K&N filter that came with it cause very little flow restriction, so no matter what future upgrade I should make to the engine, I shouldn’t have to buy a new meter, just maybe get it recalibrated for an even higher flowrate. Pro-M can calibrate an air meter to just about any flow desired, generally by just telling them the injectors that will be used so you can run a stock EEC. However, since I was using an EPEC and I could just input the calibration curve and injector size and let it figure out what to do, I had the air meter calibrated to support approximately 600 hp worth of air. This should be enough for future power upgrades. For the time being though, 35 lbs/hr injectors (dark blue - Ford production units on 1994 Thunderbird Supercoupe) were installed as they should be good enough to support nearly 500 hp at the Ford standard 39 psi fuel rail pressure.

Obviously the much larger outlet of the Pro-M air meter would not connect to the plastic elbow from the Vortech kit, so something else had to be used. A trip through the plumbing department of a local big home improvement store (Home Depot) proved beneficial, as I found a 4" to 3" tapered 90 degree PVC elbow that fit perfectly. The 4" end fit very snugly over the Pro-M outlet but I installed a rubber section of hose (also from the plumbing department) over the joint to seal it. The air meter was stuffed into the fender area that the previous parts resided except that it fit tight enough that just a few tie wraps were all
that was needed to hold it in place. This is where I noticed how much more space there is in the fender of a ’94 and newer Mustang compared to the older ones. The 3" end of the elbow aimed into the engine compartment just like the plastic piece from the Vortech kit. I used a short straight section of thinwall PVC that the Vortech flex hose would fit over and the other end fit snugly into the 3" end of the tapered elbow.

6. Camshafts - Some cams with basically stock duration but higher lift became available to try, so they were installed as the engine was being reassembled. The real SVO cams should outperform these, but were not available yet.

7. Engine Shortblock - The cylinder bores were good enough to reuse with just a light honing to take out very minor scratches so a new set of stock pistons and rings could be installed.  

8. Idle Speed Controller - Because the EPEC does not have an output for the production idle speed controller, a block-off plate was installed in its place. This has an added benefit of increasing boost slightly since the idle bypass actually connects before and after the Vortech supercharger and is almost always partially open, bleeding off some boost.

9. Thermostat - A 180 degree unit (Auto Value part number 31168) was purchased from a local auto parts store and installed. Between the EPEC programmed to turn on the cooling fan at 185 degrees and this thermostat, the engine should run much cooler this season.  

10. Battery disconnect switch - The car really should have had one of these last year since the battery was in the trunk. A Flaming River remote unit from Summit was installed.

11. Miscellaneous Engine - Otherwise the engine was reassembled just as last season with the unported SVO heads, SVO shorty headers, Vortech supercharger with 2.62 pulley, and the rest being production components.

12. The rest of the car - No other changes were made to the car from last year. So it continued with the Hoosier Quicktime 245/55/16 street tires and stock suspension with the sway bars removed as before.

First time at the track this year with the car, at Detroit Dragway on 8/4/97 ran a best pass of:
11.50 at 125.5 mph with 1.90 60 ft.

I was ecstatic, the car had much better mph than last year right out of the box! The new parts and EPEC calibration were definitely working well together to make more power. I was looking at A/F ratio during a few passes and was very impressed with the Pro-M air meter calibration because it was right on the 11:1 at 6000 rpm that was programmed into the EPEC.  

Decided to go to the track again to see if it was repeatable and to have some fun picking on the unsuspecting 5.0L Mustangs and 5.7L Camaros/Firebirds. Detroit Dragway on 8/15/97 ran a best pass of:
 

11.64 at 123.5 mph with 1.95 60 ft.

A little slower due to track conditions and the weather, but it showed that last time out was not a fluke, it really does run better than last year. I got a real idea of how mild the car looked and also how little respect the typical 5.0L driver gives to the 4.6L Mustang GT when I was in the staging lanes waiting to make a pass. A guy with a 5.0L Mustang realized he was going to race against me and noticed the Vortech whine coming from my engine compartment. He said he had installed an off-road H-pipe and a K&N filter on his late 80’s 5.0L so he figured it would be a close race. I just agreed that it would be interesting for sure, but for some reason I never saw him again after he ran his mid 14 second pass.

Decided to go to the J&P Shootout in Ontario Canada on 8/23/97 and made a best pass of:

11.38 at 125.6 mph with a 1.93 60 ft.

The car ran great when it counted - in front of spectators this time and not just on the Detroit Test & Tune nights. I even got to go a second round in the Bracket Races. This is highly unusual for me since I never work on reaction time because all I really care about is increasing the power and am not really into the competition aspect of drag racing. Actually though, I got to go to the second round because the other guy redlighted, just handing me the win. I made up for it by handing the next guy a win, but this was because I failed to make it to the starting line! Turns out that I didn’t have a really good fuel calibration in the EPEC. Goes to show that if you give a person too much control over their engine, then they are bound to do something wrong and I had calibrated the "cranking fuel" table too lean to start when it was moderately warmed up. Too late to do anything about it at the time, so I recalibrated it later. Good learning experience since there is a bit of a fine line between dumping in too much fuel and washing the cylinder walls or not enough fuel so it won’t start.  

I wanted to take some acceleration data using the Performance Trends’ Datamite hardware and software. I hooked it up to the car in the most common manner, with front and rear wheel speed sensors and a tach signal for engine rpm. One of the features of this software is the ability to obtain complete torque and power curves for the engine by just doing a single gear acceleration. Also made some real passes down the track. At Detroit Dragway on 8/29/97 and ran a best pass of:

11.73 at 124.3 mph with 2.00 60 ft.

For the single gear accelerations, I used 3rd gear because I can get completely through it in the ¼ mile and there is no chance for wheel spin. The technique is to just get the car moving in 1st then immediately shift into 3rd and make sure to lug it below 1000 rpm, then floor the throttle until the rev limiter is reached. I made a mistake and didn’t go WOT until around 3000 rpm so the following graph starts at 3500. As you can see, the engine makes good torque. The power just goes flat above 5000 rpm and is probably an indication that the stock plastic intake manifold is just too restrictive to work well with the other modifications made to the engine. I was also looking at boost during the acceleration test and noticed that it peaked out around 17 - 18 psi at max rpm. This was a little higher than expected but does explain why the engine was able to make 500 hp, and really shows that the 6 rib serpentine belt drive on the front of the engine can turn the Vortech very effectively with apparently little slip. Another thing that should be pointed out is that the results are only as accurate as the vehicle specs you input and is best as a comparative tool rather than an absolute value unless you have a good baseline that matches manufacturer's data.

The Datamite is particularly useful if you don't live near a dragstrip or chassis dyno and want to measure the effect of performance improvements. It can also be used when roadracing to keep track of laptimes and can be a real eye opener to see how much time you spend at various rpms, which is very good info when choosing what upgrades to make to your car.

Still waiting for some parts to become available so I could try them. But I just couldn’t sit around with the car running this well, so it was back to Detroit Dragway on 9/14/97 where I made one pass:

11.69 at 124.8 mph with 2.07 60 ft.

I only made one pass this time since I brought along one of the friends who helps me out a lot working on the car. I figured it was a good chance to let someone else drive it so I could take pictures and see how it looked going down the track. Matt Sweet made 5 passes in it for a best of:

12.01 at 123.1 mph with 2.19 60 ft.

He really wasn’t too far off what I had run and it gives a good indication of how easy the car is to drive. Especially since Matt is a teenager who has never driven at a dragstrip before and has a 4 cylinder Ranger for daily transportation with less than ¼ of the power. But as you can see, neither of us had very good 60 ft times.  

The new SVO intake manifold finally became available, so Matt installed it. However, the Vortech discharge tube (air passage between supercharger and throttle body) for the SOHC engine would not fit since the new intake uses a DOHC throttle body in the DOHC engine location. But, since Vortech has a kit for the DOHC engine also, the discharge tube from that kit was tried. With some easy modifications it fits well. Just to be safe, a 50 psi (approximately) fuel pressure regulator was also installed in case the 35 lbs/hr injectors were getting close to their limit. Unfortunately, even though I had the EPEC controlling the engine, the laptop computer I had been using to communicate with it was out getting repaired so I didn’t do anything to try to adjust for the higher fuel pressure.

Going to Detroit Dragway on 10/7/97 ran a best pass of:

11.27 at 127.3 mph with 1.85 60 ft.

I don’t know if even the best pass represents how good the car can perform at this point because of some problems this time at the track. On all but one pass, the discharge tube (air tube connecting Vortech to the throttle body) blew off due to the high boost. The engine also didn’t feel really responsive at low to mid rpm and felt rather flat at higher rpm. This is probably due to the higher fuel pressure causing the A/F to be overly rich, but it is better to be safe than sorry. Unfortunately, the laptop computer was still out getting repaired so I couldn’t recalibrate anything at the track. Besides, most of my time was spent reattaching the discharge tube and trying to tighten the clamps as much as possible and attempting to hold it on even more with tie wraps.

I fixed the discharge tube problem by drilling a hole at each hose clamp and inserting a self tapping screw to hold each joint together. It should be noted that there is no inherent problem with the Vortech discharge tube, but just combining the large surface area at the throttle body with the high boost I’m trying to run creates a lot of force on the tube causing it to blow off. Since the laptop computer was still out getting repaired, I decided to do what I could and installed an A/F meter and took along a stock fuel pressure regulator. Going to Detroit Dragway on 10/10/97 ran a best pass of:

11.43 at 123.1 mph with 1.86 60 ft.

The A/F meter showed the engine to actually be running lean and not rich as I had suspected. It was rich at low rpm but went leaner at higher rpm. It also seemed to be detonating at higher rpm due to the lean running. Thinking about this for a while, I figured there was a chance that the higher fuel rail pressure was causing a lower fuel flow since fuel pumps do deliver less fuel flow at higher pressure so maybe I was reaching the limit of my fuel system. Not having much else to try at the time, I installed the stock fuel pressure regulator and saw the A/F ratio improved at low rpm but was no different than before at higher rpm. This seemed to confirm what I was thinking. However, it detonated at the higher rpm a bit more because the engine was warmer now. I figured that the pistons must have broken ring lands by now after 2 passes of detonation at this power level so I just kept making passes for fun since the damage was probably done already and it was the end of the season anyway. Well, it took 5 passes with increasingly worse detonation to finally give any indication of a broken piston - sudden loss of power and smoke out the exhaust. The engine had 40 passes on it this season by now so I have to admit that the stock shortblock (including the pistons and rods) appears to be very robust as long as detonation is avoided.

Decided to do a quick rebuild if possible and try to get back out to the track because the weather was still fairly nice. Disassembling the engine showed that there was a hole in one piston and a couple others had broken second ring lands. The head gasket showed some leakage from the combustion chamber in the same cylinders but I’m not surprised because detonation at this power level produces extremely high cylinder pressures. The pistons in the other cylinders looked practically new and all the cylinder bores looked fine. It seemed that a rebuild could be done without even honing the bores. I decided to try some other pistons this time that were production pieces but had the dish in the top cut a little deeper for lower compression and also had piston pin clip grooves for full floating pins (pin can rotate in both the rod and the piston). Also installed Mark VIII connecting rods since they were compatible with the full floating pin and were the proper weight so I wouldn’t have to get the crank rebalanced. Otherwise the engine was reassembled as before.

Measuring fuel flow showed that there just wasn’t enough to support the power level. This was done by directing the outlet hose from the fuel rail into a bucket, providing a pressure signal to the fuel pressure regulator to simulate 20 psi boost, turning on the pumps and weighing the bucket after 2 minutes to get a flowrate. I decided to try out the Kenne-Bell Boost-A-Pump and repeated the procedure along with trying higher fuel pressures. The Boost-A-Pump is a very simple device that just increases the voltage to the fuel pump so that it flows more fuel. Knowing that the SVO 190 L/hr intank pump flows a lot of fuel at low pressures and makes a great feeder pump, I just hooked the Boost-A-Pump to the Vortech T-Rex pump and set it to max (approximately 17 volts). Also found the fuel flow to be sufficient with the fuel pressure raised to 52 psi instead of the Ford standard 39 psi. This made the 35 lbs/hr injectors equivalent to 40.4 lbs/hr units. Recalibrated the EPEC for the "larger" injectors.  

Wanting to see what the fuel pressure was doing along with the boost pressure, a set of A-pillar mounted gauges were installed. I bought the Autometer gauges, gauge pod, and a fuel pressure isolator from Summit.

However, after reassembling the engine, the dragstrips were closed for the season. But I eventually got a chance for a trip to a chassis dyno to see how the engine performed. Paul’s High Performance in Jackson, Michigan has a Dynojet chassis dynamometer and is quite well respected locally, so that’s where I headed with the car on 12/13/97 and made only one dyno run:

corrected rear wheel peak torque = 493.8 ft-lbs at 5300 rpm
corrected rear wheel peak power = 500.8 hp at 5400 rpm

So, it just squeaked over the 500 hp level.

It broke around 5500 rpm during that one and only dyno run. Smoke suddenly came billowing out from under the hood, so Paul shut it down as you can see on the dyno graph. Unfortunately there were some small cast iron bits on the floor. Raising the car on a lift showed a hole on the driver’s side of the block just above where the dipstick tube goes in. I was expecting something to eventually happen like this so it didn't really bother me. The disappointing part was that there was no clanging or banging noise when it happened to add some kind of dramatic effect. Only a couple drops of oil on the floor to clean up.

It appears that the real hp peak was not reached as it should peak at a higher rpm, like above 6000. Also, on the graph you'll notice that the torque curve is not really stable at lower rpm. I don't know why, but the engine was running quite rich at the lower rpm then cleared out as the rpm climbed. I had been messing with the calibration in the EPEC (you know, give a kid a toy and he'll use it) and probably just made it a little too rich. I don't think that was related to the breakage though.

Using a chassis dyno to find out what engine modifications work best on your car is a more accurate method than testing at a dragstrip since there are less variables to take into account. I should make it clear that the engine breaking was not the fault of testing on the dyno, as it would have broken anyway because the chassis dyno testing is less stressful than making passes at the dragstrip due to less time spent accelerating. Besides, the dyno is a lot easier on the rest of the drivetrain because it is all done in just 4th gear. By the way, Paul and Ronda, owners of that Dynojet equipped facility, are wonderful to work with, and hopefully we'll be hearing more from them, since they have a personal project vehicle - DOHC Cobra.

Later disassembly of the engine showed:

Cylinder # 3 had a broken piston and connecting rod. The rod was broken in mid beam and bent but the bottom half was still bolted to the crank and rotated freely. The top end was pulled out of the piston with the pin still attached to the rod. The piston top was there with most of the rings, but below the rings there was nothing left of the piston except fragments of aluminum in the oil pan.

The broken piston had come in contact with the cylinder head but didn't appear to do any real damage. There was some evidence of debris on the intake valve seat but it looks like it may not even be bad enough to require any more than just lapping to clean it up.

The rest of the engine looked good. The crank rotated freely and all the other bores and pistons looked great.

It appears that the piston broke first at the pin bore then the rod broke against the block since it was just flying around connected to the crankshaft. The piston did not break from too much cylinder pressure (boost or detonation), but appears that either one of the pin clips came out letting the pin move to one side or the piston was possibly defective and had a crack in the pin bore area.

Even though the car gained a fair amount of weight due to the required safety equipment, the new SVO hardware and Pro-M air meter worked well together to provide an improvement of .25 seconds and over 6 mph in the ¼ mile. The 4.6L SOHC engine continued to impress me with its capabilities.  

The significant stock components still in use this year include: ignition coils and wires, fuel lines and fuel rail, head gaskets and bolts, crankshaft, cylinder block, 3.27 ratio 28 spline axle assembly, and mufflers/tailpipes.

Once again this year, I have to thank many people at Ford’s 4.6L Modular Engine Engineering Department and SVO for their interest and assistance. And a special thanks to Nathan Sten, Tony Taylor and Matt Sweet for their knowledge and time spent modifying the car.

Ed Olin (EDO)
January 17, 1998

Links to other related websites:

Dynojet chassis dyno and garage facility:
Paul’s High Performance - www.paulshp.com

Performance prediction software and data acquisition software and hardware:
Performance Trends Inc.- www.performancetrends.com

Supercharger kits:
Vortech Engineering - www.vortecheng.com

Pro-M air meters and other engine electronics:
Best Products - www.pro-flow.com

Various performance parts:
Summit Racing Equipment - www.summitracing.com