Ok, so I did it. Took the plunge and bought a new exhaust and cat bypass (both Dansk)and the Autothority mass air-flow for my 87 Carrera. I have borrowed a G-tech accelerometer as well to measure the differences. I have been satisfied with its past performance. Seemed to read right-on previously with my 951 and is now giving me 185 HP values (rear wheel) for the stock Carrera. (I figure 217 stock at flywheel less 15% for drivetrain losses and a little air drag so 185HP is about right.) Adding the Dansk cat-by-pass and muffler added 5-6 HPs at the wheels (190-191 HP readings). BTW I've seen the Dansk stuff has gotten some bad comments on the posts...both pieces seem quite well built, especially the cat by-pass which has an expansion chamber (although I was expecting GHL parts when I ordered them but that's another story.) Afterwards I added the MAF. Using the exact same stretch of road, same conditions..standing start, running up thru 1st and 2nd gear to 6500 rpm or so, the finish product gave 200-201 HP. Over and over again. The MAF does give a smoother power curve from 3000 on up, but peak HP added was only 10HP on top of the the exhaust cahnges. Disappointing considering the $$ involved. Ali at Autothority was nice enough to send another chip (.203 vs. .201) to see if it worked better with my particular exhaust mods. Didnt help...same peak HP and overall, the lower RPM performance suffered. I also removed the cat by-pass. Not much difference overall...peak HP still at about 200, perhaps a bit little less torque in the lower RPM range. So, overall, a net 15 HP increase is all I've been able to get to the rear wheels. My expectation was much higher, and at >$100/HP, I dont think its worth it. Some folks may question the G-tech, but based upon what I've read, it seems to be relatively accurate, when considering the losses. ( I also had up'd the boost to +1 full bar on the my 951 and chipped it as well and got 246HP rear wheel readings, corresponding to the 275 HP at the flywheel that was expected....so I trsut the g-tech.) Does anyone else have G-tech or actual dyno data for their car with a MAF conversion out there that they can share? And if you are getting more HPs than 15 with the MAF, let me know what else you did to get it. If you are considering the MAF...use my experience as reference. The car does respond much nicer throughout the 3000-6000 range, but I've heard similar things from folks with just the chip and the standard barn-door flow meter. Thats likely my next step...returning the MAF and just trying a chip wiht the stock meter. If anyone has experiences or better yet data to share on chips, I'd appreciate it. I've seen some satisfied postings from both Autothority and Weltmeister installs. Has anyone got experience with the Rennsport chips? Steve W. seems to have had some knowledgable responses...I'm thinking of giving them a call too. Let me know.

 

That's surprising you only got 15 hp gain. That's what I would expect from a chip change and a cat premuffler. Try it with the barn door air flow meter and a chip only such as the the Weltmeister. You could also try a couple of other things to see if you could improve the result you get from the G-Tech. Try rotating the rotary calibration switch on the side of the DME to its third position,(third click clockwise from full left) This should increase fuel delivery by 3% and timing by 2 degrees or something like that. If you put back in the barn door meter, you could also try richening the mixture by opening the black plastic cover on its side and loosening it by one or two spring notches. Also closing down the turns on the idle adjustment screw. This for me has produced noticeable gains in acceleration and throttle response. Air/fuel ratio for maximum power is 12:1 and sometimes chips aren't programmed rich enough on full throttle. I would like to know your results.

 

Not surprising at all, Autothority and others have been hyping these things for years, despite the fact that every independant dyno run shows roughly the gains detailed in the original post.

 

Cal switch on DME? Please tell me more !Can this be true? More horse at the click of a switch? I must be reading or missing something...Please explain!!

 

There is a provision on the Motronic cars (944 and 911) to make small adjustments to the fuel mixture (injection pulsewidth) and the ignition timing in order to compensate for the quality of fuel available in your particular country or region.

There is an board-mounted eight-position rotary switch accessed through the little hole in the back side of the DME box. These adjustments can be made without opening the cover of the DME box, unless you have a California vehicle, which will probably have a metal plug over the hole instead of a plastic fitting. The switch has a triangular-shaped recess in which to insert a special adjustment tool — I just use a small tipped flathead screwdriver.

The switch has detent positions so you can count the clicks to tell where you are set. The DME boxes are usually set in default position #1, (stock position). The adjustments can be found in the following table:

switch position...fuel mixture adjustment...ignition timing adjustment
stock....................0.................0
2.......................+3%................0
3.......................+6%................0
4.......................-3%................0
5........................0................-3 degrees
6.......................+3%...............-3 degrees
7.......................+6%...............-3 degrees
8.......................-3%...............-3 degrees

 

Steve,

Does this mean if you are in position #3, the length of time the injector sprays is increased by 6%. In theory then, the cylinder is receiving 6% more fuel on each injector pulse than in the "stock" position #1.

This all sounds very good , but what is the downside (if any)?

Thanks, Bruce

 

Bruce,

Yes, position #3 will should increase injector timing by 6%, thereby enrichening your air/fuel ratio by 6%. The area that is really affected is in the preprogrammed air/fuel maps where the O2 sensor signals are ignored and the DME relies strictly on its maps. Such an area is on full throttle acceleration, where a microswitch is engaged on the throttle body when your throttle butterfly is opened past something like 75%. I believe it also affects the idle and mid-throttle driving, but your O2 sensor will attempt to compensate for any misalignments trying to keep it at the stoichiometric ratio of 14.7:1.

A 3-6% increase is a small, but good amount to compensate for any lean condition as a result of small performance enhancements you may have done to your car such as on the exhaust or intake. Beyond that, you can play with the fuel pressure regulator to increase the fuel pressure. You would do this by removing the regulator and pressing it down a little bit in a press - increasing spring release pressure. In my tests, fuel pressure increase to injector flow increase is 2:1. That is a 10% increase in fuel pressure increases fuel volume by 5%. It could be 3:1 but I don't remember because I did those tests 10 years ago.

 

Thanks for the reply and ideas, Steve (and others). Barn door and stock air box are going back on. Weather is turning poor here (upstate NY) so I dont know if I'll get much 'testing' dialing in the DME yet this fall but I'll give it a shot. Steve, are you running a chip with these changes and if so which? Thx.

 

What is the effect of turning this switch on a DME modified with an aftermarket chip?

I have no idea what kind of chip is in there - just that it's in there. I know for a fact though that it raised my rev limiter significantly, to something like 6900rpm

 

Mark, you probably already know this, but be careful with a rev limiter that high. I have emailed with Steve from Rennsport systems in Portland, OR (not Seattle) about this in the past and he said that the con rod's and the valve train is the weak spot in the 3.2's. If you notice the '88 clubsport had different intake (or is it exhaust) valves so they could raise the rev limit on that car to 6840, I think. Weak rod bolts and weak valve springs and retainers can make for a very expensive problem. Just thought I'd throw that out there "in case."

 

I have an 89 3.2 with cat bypass, GHL single outlet muffler (great sound!), and Autothority MAF kit. I have dyno tested it at 212 rear wheel HP. (Dynojet inertia dyno). If you figure 15 % drivetrain losses, that figures out to 249 engine HP, or an increase of 249-218= 31 hp over stock. I am VERY happy with the car's performance. MY DE instructor at the glen (who races an '88 in PCA stock class) says my car runs up the back straight like a "scared jack rabbit".

 

Peter, have you ever tried a G-Tech on your car? I'd be interested in the comparison WRT your dyno results. I guess with the cat by-pass and sport muffler, I still might have expected more that 30 hps, based upon ads. Ive seen advertisements and have toalkedto folks that state values for a 'true' 30-38HPs (at the flywheel) for the just the MAF kit.

 

Hi All,

I just bought a '87 Targa which had a full rebuild 10k miles ago by the previous owner. It has a 964 cam, Autothority chip, Euro pistons and SSI headers with the double-tube sports muffler (no cat). It sounds great. I have the dyno chart from a PCA Dyno day showing 219 hp at the wheels. Here is the link to the dyno day website. Mine is car 12. http://www.hcrpca.org/pictures/20010...y_results.html I am sure the internal mods make up most of the increase. What is noteworthy is that the only non-turbo car on that day which had more horsepower (222hp), despite some issues, had the mass airflow meter. The page is worth a look to get an admittedly non-scientific view on what mods do what on the dyno. I will get a G-Tech Pro in the near future so I can compare.

 

I took the MAF back off the Carrera, and re-installed the 'barn door' and did some more runs. HPs returned right back to the 191 HP value, down from the 201 HP values. Note the Dansk exhaust is still on which gives the x-tra 5-6HPs over stock. Yeah, the car loses some lower RPM torque, but the difference isnt big, but I still plan to get a chip. Still looking for the definitive performance chip suggestion. I called Perf Products on the Weltmeister and it sounds as though they are discontinuing them and moving to their own branded chip. (although they could still take my order for the Weltmeister, the guy made it sound like they werent in stock.)I havent had a chance to try Steve Wong's suggesting of adjusting the mixture/timing switch in the DME, but its on the list....perhaps this weekend. I also did some more 'testing' of the G-tech. I friend of mine purchased a 2001 Mustang Cobra a couple of months ago and I'm letting him borrow it to get a new reference point. The car has 320 HP out of the box, at the flywheel. There are a number of posts around citing measured 272 HPs at the rear wheels on dynos. We did a quick a couple quick test runs today, properly accounting for gas and passenger weight...we got 268 HP. He's going to do a series of runs and give a better averaged value, but I'm convinced the G-tech is pretty accurate.

 

Herb,

Is your dansk a single or dual outlet? I had intially installed a dual in- single outlet dansk (along with SSIs). sounded really nice, but not much difference, if any, from OEM exhaust. Less than one year later, I installed a dual in - dual out dansk (which was the original plan, but couldn't locate the dual out at that time).

There was a discernable performance (and interior noise) differnce with the dual outlet dansk exhaust. I don't know (and don't care) what the HP numbers were, I know that there was a difference because I could feel it (after driving the same car for 15 years you kind of know what faster feels like). The engine revved more freely and zoomed up to (and past) redline so easily that you had to be careful (rev limiter disconnected). I was not displeased with either dansk exhaust. The mufflers fit just like OEM and I kind of like the different look of the "swept back" tail pipes. One look at those pipes and you know that's not stock.

BTW, where are you in upstate NY? I'm in Rockland County (about 20 miles north of NYC).

Richard
'87 Carrera (soon to be 3.6L ... by the end of this month).