curious people have been here...

Since it's raining out, I decided to write a book...

The Car: 1988 Merkur XR, 5 speed

Well, I'll admit it. I didn't believe it when several people said the 87-88 Turbo Coupe IHI turbo was a restriction on the top end. I was basing my disbelief on the size of the turbine side, and the strong midrange. But, the compressor side must be a bottle neck. I disbelieve things, until I see it for myself. That's what drives me to build some of the engine combinations that I do. Here's one of my latest combinations:

As some people know, I bought a 1988 5 speed XR at Carlisle last year. This car was a street turd. It had a Max Flow turbo, and a custom built 3" exhaust, but no intercooler. The cooler temps, out of the bigger turbo, allowed it run 18 psi of boost, but it took a while to spool up. Not much fun to drive, unless you had lots of road.

Since my Ranger Turbo was down for reincarnation, I stole the IHI turbo off of it, and put it on , along with Nick's Mass Air, and one of my ported exhaust manifolds. YOW!!! What a difference. The IHI turbo makes boost NOW, and with the Mass Air conversion it could really gulp in air quickly. The Mass Air requires some twiddling to get it right, but IMHO is a good improvement.

I also installed an old small Spearco intercooler that I had laying around. I've installed this thing on most every car I've owned, when I need to install an IC in a hurry. It doesn't flow a bunch, and it was mounted in a position that most people would laugh at, but it eliminated the detonation I was getting after I switched turbos.    It had 2" piping with several ugly 90 degree bends. At this point, I could run 18 psi out of the IHI, and it ran pretty strong.

The car ran strong in the low rpm, midrange, and pulled well under full boost, so I figured I'd put it on the dyno, and see what it was really like.

Dyno Pull 1: Turbo Tek Toys "Hot Street 3" cam, advanced 4 degrees, stock 88 XR 5 speed F3D processor, mass air set leaner than the nominal setting, and ~18 psi of boost.

Result: 198 HP and 264 LB/ft torque, 227.7 HP and 303.6 LB/FT torque at the motor.

Observation: Hmm,  no topend on this motor.   But corrected to the engine, this is dead on with a stock 5.0 HO's ratings! 

Pull 2: richened up the mass air a tad, and retarded the cam to the straight up position.

Result: 203 HP and 273 LB/ft torque, 233.4 HP and 313.9 LB/FT torque at the motor.

Observation: Fattening up the mixture really smoothed out the power curve. The power curve moved up very slightly due to the cam change.

Pull 3: Installed a Superchip for a PF3 with the PE table in it. This effectively makes the car act like it has a PE with a 7000 RPM redline. Note that the program is changed slightly by Superchips, from a stock PE. I believe it has a smoother timing curve and more fuel. You can make your own determination as to whether or not it is worth it.

Result: 215.5 hp and 283.5 LB/ft torque, 247.8 HP and 326 LB/FT torque at the motor.

Observation: There was a hint of detonation on this run, even though you don't see it in the dyno curves. The motor felt like it was on the ragged edge. Personally I'd give up the power, and remove the Superchip, in the interest of longevity, and the ability to run variable grades of gas.

These results are as measured at the wheels, add the industry standard 15% for the numbers at the engine. 93 octane pump gas was used, with no octane improvers added. All three runs were made within 15 minutes of each other, so, a proper cooldown could've produced more power on the later runs.  I also believe that more careful tuning after stage 2 could've made additional power, but I moved on to testing the Superchip instead.

Summary:

1) This car is a hoot to drive on the street. You shift below 5000, and scoot around everybody. Because of the exhaust, it's also pretty quiet, even under max boost.

2) The torque curve turns down at 4000 RPM. This is undoubtedly because of the the IHI turbo. Ok, I believe, now. :)

3) I already have changes underway on this car. However alot of people would be very happy with the current combo and keep it just like it is. It idles nice, gets good mileage, and the throttle response is instantaneous. In town, or on the freeway, passing one or several cars, or just staying way ahead of traffic, is only a 1/4 throttle away.

4) People chase hp numbers, yet ignore torque. Regarding the 2.3 turbo, this is a mistake. Because of the constricted high rpm flow of the stock components, no 2.3 turbo will ever make as much hp as torque.

Math lesson: Horsepower is torque times axle speed divided by 5252. On a chassis dyno, hp is EQUAL to torque at 5252 RPM. So if your torque curve falls off, at or below 5252 rpm, you will not make as much hp as torque.

Since I made low torque at 5252 RPM, I had a low horspower number. However, at the flywheel, I made peak torque of 326 LB/ft at only 3500 RPM. In comparison, an 87-93 Mustang HO 5.0 makes 300 LB/ft of torque at 4000 RPM.  I made 247 hp at the flywheel,  which is more than the 5.0s 225 hp rating. But, why did I make more hp than a V8? Because, I made *a little more* torque at a 5252 RPM.

Note that the XR made more than 210 lb/ft of torque from 2850 to 5000 rpm, with a max of 283.5, at the wheels.

5)  It's important to note what is stock on this car; all the ignition components, the fuel pumps, the injectors, the fuel pressure, the head, the intake, the valves.  It didn't have; a big turbo, (in fact the opposite) a decent intercooler, or even a decent intercooler location.  I have no idea what the timing is set at...

6)  How fast is it in the quarter mile?   I don't know, or care.  It squirts.  It's a fun car to drive.  It will definitely pull a good 0 to 60 MPH number.  If I had to guess, I would say that it could probably run a 14 flat, or better, but the mph wouldn't be impressive.  This is based on the fact that Chris Thomason has eek'd a 13.7 @ 103 out of his XR.  See comparison below.