Where is my 95 Miata's Horsepower?

[oe_tuner]

I finally got my car to the dyno last week. I was able to dial in the A/F a bit to get rid of any lean spots. The blue line shows the lean condition I had at the bottome end. I did end up with a rich dip around 5500 RPM that I cannot seem to get rid of. This shows up on the dyno too.

http://www.flickr.com/photo_zoom.gne?id=772103397&size=l

I knew going to the dyno that the car did not feel as powerful as I was expecting. The dyno confirmed my suspisions. Peak HP is less than 175 and torque is around 140 lb-ft. All pulls were done in 4th gear. The dyno is a Dynojet. I have been over everything (fuel system, ignition system, timing, compression check, e-cool function) to make sure all is in very good working order, so I do not know why the power is off by 20-25 hp. Today, I even pulled the cat off to make sure it was not plugged. It looks like new inside. I do not know how to make sure the exhaust is not plugged up, but I do not really think it is anyway. There are no rattles and the exhaust sounds like any stock 95 Miata. The car only has 57K miles on it. I have 10.5 PSI boost at peak, my AF is around 11.5 to 12.0 accross the board except for it tapering down to 10.2 at 5500 RPM then rising back towards 12.0 at redline.
Also, most of my PCPro settings are max'ed out just to get my AF around 12.0
My final settings are:
0-2800 - 8
2800-5000 - 6
5000-7000 - 7
Yellow/Blue & Red Blue - 7.5
E-Cool - 8
Any ideas where my horsepower is hiding???

[socal pat]

I know you said your fueling is fine, but since you have to max out the PC-Pro settings to run 12:1 I'd keep looking there. What are your fuel pressures under boost at 3,000 and then at 6,000? As Tom said they could drown Dan's car in fuel if they wanted too. I know on my 2000 I mistakenly turned my E-cool too high and when I went into boost it bogged so badly it almost killed the motor. Who knows? Could be a fuel pump, regulator, even iffy injectors.

[BlownMX5]

+1 on fuel issues. On my '94, if I ran PC-Pro numbers like that, IF it ran at all it would be so, so rich. I have stock injectors and a 190lph pump. Do you have a dyno chart that shows the a/f instead of boost?

[FormerDatsun510Man]

For starters, if you didn't have that dip that starts at 5300rpm it looks like your setup would hit 180rwhp. I would figure that out first. Is it the beginning of ping? Or is it because of a sudden change in a/f ratio? If it is the later I would smooth the a/f ratio out more. You can do this by messing with the mid rpm and high rpm fuel settings... carefully of course. Unfortunately, this means going back to the dyno again. While you are there you can also try moving the entire fuel curve 1 step at a time and see what happens. It might start picking up power. Just don't go leaner than about 12.7-12.8:1. Finally, check the ignition timing. You might want to make sure that it is indeed at 10 deg BTDC at idle and that it picks up properly with rpm with the car on the dyno.

Also, importantly, make sure the engine can cool down for about 5-10min between dyno runs once you get it close to tuned. You can easily lose 10rwhp when doing runs back to back with little break. One trick is to let it cool 15-20 minutes after it is all dialed in and do a glory run or two. :)

Bill

[FormerDatsun510Man]

One other thing, what pulley are you running? With a 105mm I would expect your setup would be in the 180rwhp range given the fact that the '99-'00 are dynoing in the 190rwhp range with that pulley.

Bill

[Tom @ Fast Forward]

Even with a 105mm he should be in the low to mid 190s.

[oe_tuner]

Thanks for the responses.
Here are some captures from my AF data logging I did during the final dyno pull.
The vertical white line is the point in the graph that matches the numbers on the right side.
http://www.flickr.com/photo_zoom.gne?id=780760023&size=o
http://www.flickr.com/photo_zoom.gne?id=780760093&size=o
http://www.flickr.com/photo_zoom.gne?id=780760371&size=o

My concern with "fine tuning" is that with my current AF curves and only 3 RPM ranges to adjust, there is not enough resolution to fine tune my rich dip. If there is a way, please enlighten me.

As far as my fuel system goes, I am extremely confident that is is working correctly. I have a new Walbro 190 L/h HP pump, a new OE FPR and a new Fuel Filter. I have tried 3 different FPR's and all had the same performance. I have tried 3 different E-cool injectors, all with the same results. I have verified that the e-cool functions when boost is applied by putting about 5 psi on the boost tube when the car is at idle and the car stumbled. The main PCPro was verified to work in the same manner. I also have a fuel pressure gauge in the car and it reads a constant ~40psi throughout the rev range. This is the correct pressure for a 95 according to the 1.8 Enthusiast Manual. If I clamp the return the pressure spikes to 90+ psi. Other than my main 4 injectors and steel lines, the entire fuel system has been replaced and verified.

I have confirmed that my base ignition timing is 10 degrees.
I have checked my coils and plug wire and they are all perfectly in spec.
The Plugs are of course new with the kit and the gaps are also perfect.
My compression check was also excellent.
The car only has 57K on it. And it was pampered by the previous owners.

At the Dyno we did wait a bit between runs. Heat soak was not an issue. In fact the power increase with each pull. We also had a big fan blowing on the front of the car and the hood open.

As far as horsepower expectations, I expect to get what is advertised with the base kit (which I have) which is 195 WHP minimum (at Tom mentioned above). 180 is not what I expected. I could have saved $1500 and bought a Jackson kit if 170HP is acceptable. Of course the cold side offers some drivability benifits, but regardless, I am really hoping to meet the expected 195HP on a dyno jet.

I did a timing belt service at the same time as the install. I feel pretty confident that nothing was off a tooth. The car runs like a top. Idles great, runs smooth, pulls smooth, drives great on the highway. It makes good vacuum at idle (~18in.Hg) Is it possible that is would run so well if the intake cam was off a tooth? I am sure the exhaust is right, since the ignition timing was not off when I was finished. The only problem is that the car is just not quick like was expected, and the dyno has confirmed what my seat of the pants was telling me.

If any one has any ideas, please let me know.

Thanks!

[Tom @ Fast Forward]

Well, you certainly have no shortage of fuel if I read those charts correctly. The first one looked the best but they all looked like they could use a wee bit less fuel. But that would account for only a few WHP.

If you have 10PSI or more boost, 11-12 A/F, a free flowing exhaust, good compression, proper valve timing and proper ignition timing with no ping, you should easily be over 190 (advertised minimum) WHP.

We put an adjustable cam gear on my 99 for test and it would run just fine with the cam gear off the equivalent of 1.5 teeth either direction. As a matter of fact, screwing up valve timing can make it idle even better. However, causing loss of power up top.

The main culprit we have seen for loss of power when all else is good is exhaust. What goes in must come out.

That little 1.6L made 178WHP with a 105mm pulley and it was blowing past the rings. If the rings were better, I think it would have come close to 190 with a 105mm pulley and base timing is dropped to 5 degrees to avoid ping. With 10 degrees, I'm sure it would have been 190. We are going to drop it to a 95mm pulley and it will probably still make 170+. It also has a significant dip ~5500 but it didn't effect max power.

When we put a car on the dyno, we almost always do a with and without exhaust to see what the changes are. Best way to check the cat.

I can't tell from those graphs, how much boost do you get at start (WOT at 2500RPM, for example) and at 7000 RPM?

[BlownMX5]

Is there really that much difference between c/s and h/s boost? My '94 hotside might get close to 8psi with my 105mm pulley once in a while. That's based on what my Zeitronix is telling me. I wonder if having the boost sensor mounted in the DTB is really a good thing? On the coldsides, there are ports for sensors built into the IM, right?

[Tom @ Fast Forward]

We alsofound that the 1.6L hotside we were working on used a port on the IM right at the DTB for boost pickup which is where it was for the JR M45 kit. We were getting 5-6PSI and knew it had to be more. We moved it to a port used for the FPR (TEE into that line) and the boost read ~11 PSI. It is hard for ANY control card to properly correct for fuel if the boost is 11 but the card thinks it is 6.

Here is the other thread on the BRP/SOT kit. http://www.fastforwardsuperchargers.com/forum/showthread.php?t=553&highlight=dummy

On the other hand, the hotside can be 2-3 PSI less simply due to losses in the outlet manifold and IC. If it is a straight crossover pipe and the new outlet manifold, the boost pressure should be real close for the HS and CS.

[BlownMX5]

I guess what it comes down to is would the Zeitronix boost sensor behave the same as an actual fitting that is sending air to the PC-Pros? The effect you're referring to involves a true vacuum/boost fitting being poorly positioned relative to the air flow. The Zeitronix boost sensor is totally electronic and really doesn't have to deliver air anywhere. However, if this phenomenon occurs with it as well, then my datalogs might be reading low also.

[oe_tuner]

I can't tell from those graphs, how much boost do you get at start (WOT at 2500RPM, for example) and at 7000 RPM?

Tom at 2500 I am making 5 psi
At 6700 - 10.5 psi
The boost builds in a perfectly straight line between those points
The Dyno guy had a zeitronics boost sensor hooked up to my car and got the same results as I did with my boost sensor.

I think I will be pulling the valve cover when I get a chance to see if I am off a tooth on the intake cam.

Like I said, the cat looks like new, I can see light through all the little holes.
Maybe the exhaust is plugged, but I really doubt that. It sounds fine and does not have any weird rattles or anything.