B6 Horsepower Speculation

[Safety Guy]

I'm taking a break from my front suspension to post this simply because I can.

Here's what I'll be winding up with after I'm finished with my B6 swap into Luxstiva. Please assume it will start and nothing blows up.

B6 SOHC 8 valve engine from a '94 323, rated at 82 hp.

-FMS header
-Magnaflow cat and
-muffler, both with 2" inlets and outlets
-2" exhaust pipe
-'91 Protege 55mm TB mounted on port-matched B6 intake
-balanced set of injectors
-cold air intake

I know folks like to add too much to each mod when they figure out their supposed horsepower gains and I don't want to do that. Note that most of this stuff is strictly "stage one" but it should work together for better air flow.

I'll be conservative and assign one horsepower to each mod. Keep in mind I'm not saying each mod adds "exactly one horsepower." I'm saying that I think each mod working together with the others should end up adding about one hp average.

My guess is that I'll have 7 additional hp for a total of 89 hp.

What do you think? Am I being realistic?

Karl

[Tim]

That sounds realistic.

The FMS header should make a significant difference in the amount of power the engine makes.


Regards,

Tim

[Safety Guy]

If you ask me, I really think I'm being conservative here. My guess as to a maximum hp number would be around 94 or so.

I'd say I'll have from 88 to 92 hp compared to a stock B6's 82 hp.

With an automatic of course. I want around 90 to 96 hp. I don't really want to go over that to keep my fuel economy good. My goal is "competent performance" not "all out performance."

Plans for this spring include maybe some more intake work, hooking up the A/C (which will take away a bit of that hp) with the proper crank pulley and belt, the Aspire suspension swap with manual rotors, and 165/70-13 tires on Aspire factory alloys.

For better handling, I may get some 13 X 5.5" alloys with 185/60-13s.

I'm also going to investigate going to a newer (or rebuilt) Aspire ATX with lockup torque converter so my 165/70s and 185/60s will be closer to "speedo reality" and to give a bit better pickup (4.0 final drive vs. 3.8, IIRC).

Karl

[Silv3rBull3t]

I think you will have closer to 90hp at the wheels with the right timing setup... But with the Auto I think you would still feel underpowered comparably to a 5 spd... IMO -Kyle

[Safety Guy]

Ah, 90 hp at the wheels would be great! I'm talking about at the crank though. Parasitic loss via drivetrain would be what--about 15 or 20 hp? With these lowly mods, 90 at the wheels sounds high to me.

The 5 speed comes later, in another car: first a "higher performance" B6 swap, then a few years later maybe a BP or a supercharger added to the B6. My goal then will be around 130 to 160 hp. I don't think I'll want more than that.

Luxtiva is for "Luxury Festiva" That's why I need the A/C eventually.

After I do two B6 swaps I figure I'll be ready for something a bit more challenging.

Karl

[Silv3rBull3t]

Well with Festiva trannies the parasitic loss seems to be much less, just look at Wil's dyno chart (stock Festiva almost put down the actual Crank rated HP) so I would assume HP loss is much more like 5-8hp and making the car breathe that much better will help a good bit at different points on your engine's rpm so overall the feel will be much better even though it may not be quite as high as 90whp... I do believe however upper 80's should be achievable... -Kyle

[FB71]

Keep in mind that a manual trans with very low rotating mass presents a lower parasitic loss than an automatic trans, due to the large increase in rotating mass, ie, the torque converter. Additionally, a manual trans does not have the added drag of a fluid pump, used to provide working hydraulic pressure to actuate bands and clutches.

I would estimate an auto trans (Festiva/Aspire) presents a loss of about 10-15hp, erring on the high side.

That being said, Karl, I believe your initial estimate of 89hp to be low. Increased scavenging (at higher rpms) from the header and exhaust, coupled with a less restrictive inlet and a colder air charge and properly flowing injectors, I believe would yield around a 15% increase in peak hp, or about 94-95hp. However, I suspect there will be a down side. Less restrictive exhaust and inlet cause stalling of the air charge and waste gas flow at low rpm, due to larger volume in which to fill/expand. That means that your peak hp and torque #s will occur at a higher rpm than stock. So, while I believe you experience a significant gain in power at speed, I believe you may experience a slight decrease in performance at very low rpm (accel from stop). I wouldn't expect to win a drag race, but it should be a blast to merge on the highway!

[Tim]

Keep in mind that a manual trans with very low rotating mass presents a lower parasitic loss than an automatic trans, due to the large increase in rotating mass, ie, the torque converter. Additionally, a manual trans does not have the added drag of a fluid pump, used to provide working hydraulic pressure to actuate bands and clutches.

I would estimate an auto trans (Festiva/Aspire) presents a loss of about 10-15hp, erring on the high side.

That being said, Karl, I believe your initial estimate of 89hp to be low. Increased scavenging (at higher rpms) from the header and exhaust, coupled with a less restrictive inlet and a colder air charge and properly flowing injectors, I believe would yield around a 15% increase in peak hp, or about 94-95hp. However, I suspect there will be a down side. Less restrictive exhaust and inlet cause stalling of the air charge and waste gas flow at low rpm, due to larger volume in which to fill/expand. That means that your peak hp and torque #s will occur at a higher rpm than stock. So, while I believe you experience a significant gain in power at speed, I believe you may experience a slight decrease in performance at very low rpm (accel from stop). I wouldn't expect to win a drag race, but it should be a blast to merge on the highway!

Based on what you said, could the decrease in performance at low RPMS be overcome with different camshafts?


Regards,

Tim

[FB71]

to reoptimise low rpm performance, the cams would have to become more conservative (less lift/duration), which would defeat the other components entirely. We're not talking about (or, aboot, for our Canadian readers, eh) a drastic loss in power, or a major shift in rpm. Karl has kept the mods conservative, minimizing the change. I just wanted to point out that there will be a change.

[Tim]

to reoptimise low rpm performance, the cams would have to become more conservative (less lift/duration), which would defeat the other components entirely. We're not talking about (or, aboot, for our Canadian readers, eh) a drastic loss in power, or a major shift in rpm. Karl has kept the mods conservative, minimizing the change. I just wanted to point out that there will be a change.

In other words, the change will be so slight that it's not worth messing with?

(taking notes for upcoming B6 swap...)


Regards,

Tim

[FB71]

the increase in power will be noticable, but the shift in rpm where the power is made will be less noticeable, but not invisible.

[Tim]

the increase in power will be noticable, but the shift in rpm where the power is made will be less noticeable, but not invisible.

Ah.

So to overcome it, put the pedal to the metal!


Regards,

Tim

[FB71]

bingo! :twisted:

[jeffdjeffd]

That's pretty much what I've experienced, Jim. Above about 3500 RPM it throws me into the seat.
jeff
B6/ATX