More HP for a K75 (& K100)

Cheap HP for the K75

Greg Hutchinson, president of the BMW Club of Northern California turned me on to a means of getting more HP and torque recently. I installed this upgrade this weekend and was rewarded with an obvious increase in HP and noticeable performance boost.

Apparently a number of years ago a couple of engineers, I believe he said from Bosch and TRW found that a set of Ford fuel injectors with a different spray pattern from the stock BMW gave an increase in HP and torque. Greg told me this was proven in dyno tests and I have to agree with the results. My own ÔÇ£seat of the pantsÔÇØ experience is that there is a noticeable increase in performance especially at and above 4k rpm.

This was a very easy upgrade the hardest part was parting with the $160 for the injectors. The installation was easier than I thought it would be with the hardest part being stopping the gas flow from the fuel line to the fuel injector rail. I used a small clamp and the whole process took less than 15 minutes and I am not that mechanical. I got them at NAPA Auto Parts $54 each (Ford has them for $94...)

Note that I also was told that there is an increase in gas mileage but I didnÔÇÖt see this on a 163 mile trip as I think it was because I was a little aggressive on the throttle.

I donÔÇÖt have the part number on me at the moment but I will reply to emails and post it later or tomorrow.

Paul,

FORD:
'92-'94 4.9 6 Cyl F1ZZ9F593 B

Is this the part number?

Yes

I believe it is, I will have to double check but it looks correct.

Have you ever had your old injectors ultrasonically cleaned? They don't flow too badly once 10 years of varnish is removed.

http://www.trademotion.com/partlocator/index.cfm?siteid=213787

$50.80 each at above link.

paulsibek said:

Cheap HP for the K75



Note that I also was told that there is an increase in gas mileage but I didnÔÇÖt see this on a 163 mile trip as I think it was because I was a little aggressive on the throttle.

I donÔÇÖt have the part number on me at the moment but I will reply to emails and post it later or tomorrow.

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After a few more tank of gas please let me know if this helps your fuel mileage. If it does do all that then I will make that upgrade. Thanks

Gas Mileage

I didn't do this for an increase in mileage although it would be nice if there is. I was told by Greg there is.

I am willing to trade of a mile or two a gallon for the performance.

If I see an increase I will post it.

I'd sure like to see side-by-side dyno results. I suspect that any noticable increase is more likely due to comparing new injectors the with old OEM units. Cleaning the OEM injectors would probably produce almost the same performance improvement.

I think it's important - that dyno tests be done double-blind (the tester doesn't know what injectors are in the bike for each run).. and they be done back to back, same day, same bike, same weather, same fuel, etc. Also as others noted - new to new injectors if you want real data.

I find it hard to imagine the mechanism that a differing spray pattern can give more HP by since the intake valves are closed when the injectors spray.. and the vapor/mist sits there until the valve opens and it's sucked into the cylinder. But hey - if the dyno results - done as above - prove it works, it will be the only thing I've heard of besides a turbo that actually gives more HP from a K bike engine.

We've been down this path before.. When I first did this swap after the Flagstaff National, I had the 3 different dyno printouts that showed the different, progressively, improved curves. I had maybe 15K on my original 1987 K75 when I went from stock, to CC Products imjector upgrades (BMW 318i units) to these Ford units. I don't think I had enough miles on the engine for so that dirty injectors factored into my results. That paperwork was long gone when it was brought up here again a few years ago. Same arguments.. but no proof. If you can find an old CC Products catalogue, Chris has a printed dyno comparison as part of the parts discription.

So this time,, who has access to a dyno and a stock, low milage early model K bike?

beemerguru said:

So this time,, who has access to a dyno and a stock, low milage early model K bike?

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No dyno, but I've got a stock K75/2 with about 10K on it. It's so stock it still has those horrible wheelbarrow handlebars.

Injector Flow Rating?

Does anybody know what the Ford injector flow rating is and how it compares to the stock BMW injectors? I'm a small block Ford enthusiast and know that there is often more power available by increasing the injector size (flow rating) and also sometimes by decreasing the injector size, all of it depending upon other engine mods. Bruce

Kayseventyfive said:

No dyno, but I've got a stock K75/2 with about 10K on it. It's so stock it still has those horrible wheelbarrow handlebars.

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Bound to be a place in LALA land with a bike dyno..see what they charge for 2 runs for this experiment.

If anyone in the NY metro area has a K75 and the urge (and $$ for the injectors) - I do have access to a dyno..

Injectors

Fitted the Napa Ford injectors to my 30k mile K100RS.
It seems to have corrected, what I felt, was a lean running motor (by design, I'm sure).
Throttle response is 100% better, blip the throttle and the response is instant.
The boost from 5,000 rpm feels like a supercharger kicking in.
When warming up it smells rich, havent ridden enough yet to see if economy/range has been hurt.
Also, I've done a little arthroscopic surgery to the stock exhaust system to relieve back pressure which I feel helps at the higher rpm range. Makes the exhaust note, under load, a little raspy.

Mark,

I have a 91 K100RS also. I am very interested in how your fuel economy is affected by the new injectors. My exhaust smells rich when cold also with the stock injectors but the bike gets 50 mpg at a steady 70mph cruise so I'm not complaining. My computer has a 'chip' in it that was installed by the previous owner, don't know any more about it other then it's there. I also have a lean surge with light or trailing throttle at 3500 rpm. Bruce

Another Thing

I noticed is that there is less backfiring.

I had replaced all the little rubber things and felt that the cause was the Staintune, my mech concurred.

Now I get a pleasant burbling and a little popping when I don't close the throttle all the way but no more backfiring.

My mileage is suffering from a overactive throttle hand as I like the power from 4k on up. I commute 60 miles a day and use the power to accelerate in places where I need to powerup between cars or get out of a blind spot. Also I have four long up-hills and now have power to pass without downshifting.

Definately a worthwhile upgrade.

paulsibek said:

I noticed is that there is less backfiring.

I had replaced all the little rubber things and felt that the cause was the Staintune, my mech concurred.

Now I get a pleasant burbling and a little popping when I don't close the throttle all the way but no more backfiring.

My mileage is suffering from a overactive throttle hand as I like the power from 4k on up. I commute 60 miles a day and use the power to accelerate in places where I need to powerup between cars or get out of a blind spot. Also I have four long up-hills and now have power to pass without downshifting.

Definately a worthwhile upgrade.

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What model are we talking about? The StainTune for the K75 was awful - takes a full 33% of the midrange power away, to give you about 1HP at 7K RPM.. (and if you check my website - the dyno runs, repeated runs on multiple bikes are there.. http://www.eilenberger.net)

deilenberger said:

What model are we talking about? The StainTune for the K75 was awful - takes a full 33% of the midrange power away, to give you about 1HP at 7K RPM.. (and if you check my website - the dyno runs, repeated runs on multiple bikes are there.. http://www.eilenberger.net)

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That reminds me of my old bike and the Luftmeister exhaust the PO had put on my old K. He was proud of the kick it gave at 3,500 RPM or so. What he didn't realize is that what he was really feeling was a loss of low end power.

Which exhaust

do you recomment for more power?