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Discussion Starter · #1 ·
I've seen cylinder bias mentioned in the forum a lot. I recently did a once over on my 95" '03 FLHRCI, replacing the SE204 cams with TW37G, and getting the heads ported by AMS. Had a SERT installed, and a dyno tune done by the dealer. Even though I asked for the cruising range tune along with the full-throttle runs, they didn't do it, as the only cells that were changed in the base map were the 100% throttle, 100 kPa columns, and some minor stuff in the spark advance at low throttle setting. Now i'm having a go at it to improve the mileage. I look at the map the dealer used as a base. 105HG018-D0, which is recommended for FLH with 95", forged high-compression pistons, SE257 cam, SE high-performance heads, etc. There's a map (105HD019-D0) for 95" Softail, cast flat-tops, stock (or performance) heads, SE203 cam. With my cast flat-tops, TW37G, AMS heads, I think I'm closer to this setup, so I took the full-throttle part of the dealer's map (AFR, cylinder VE's, spark advances), and pasted it into the Softail map. Mileage jumped 7 mpg, I think it's because of timing. Now I'm doing plug readings trying to tweak the AFR, but the rear cylinders VE numbers seem really low. Question is why there's so much difference in VE between front and rear cylinders (front VE is much higher, more fuel)? I know we're trying to fool the ECM, but I've always heard the rear cylinder runs leaner and hotter. Don't we want to richen it up? Also, the two maps I'm using have big differences in spark advance at cruise. SE257 map is 34 degrees at 2500 rpm, 50 kPa, softail map is 43 degrees. I don't get any pinging, and SERT shows no knock retard. Any scientific theory on this stuff?
 

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I don't even know where to start on this reply.

First, what static compression did you get setup? What pipes are you running?

To do cruise VE and spark requires a dyno with a load brake, did the dealers dyno have one? Not all dynos have a load brake.

There is a right way to tune with the SERT and I hate to tell you but it ain't happening in your case. The maps that you think "are close", aren't!
There is a real danger of getting a lean spot and damaging one or both of your cast pistons.

My custom map bears zero resemblance to any canned map that is on the SERT. Yes, the front cylinder has higher VE's but you really can't tune the motor without AFR numbers and monitoring the power output. Then the ignition tables get adjusted monitoring power output with VE tweaks where needed. You have to monitor AFR in each cylinder independently. To avoid detonation, VE and spark go hand in hand, it's a balancing act. You can use the knock sensor in the Data Mode to see if it is being engaged or not. If you are too advanced down in the idle range or low rpm, low load, the CHT gets hot in a hurry.

The bottom line is, I would recommend that you seek out a knowledgeable motor wrench that knows the SERT and has tuned 95's with the 37 cams and pay them to tune it right. It will save you a lot of potential aggravation down the road.
 

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Discussion Starter · #3 ·
AMEN brother! I understand, cause I'm living it right now. I "sat" a long time, trying to decide whether to do anything with the setup that I had. That was Stage II Big bore, but with SE204 instead of 203. Wanted a gear drive, cause my chain tensioners flew out the motor and busted me on the chin. :whistle: Figured the best thing to do was the SERT, cause it's the most flexible. Trouble is, it's the most flexible! :unsure: I've even looked at buying a Dynojet 250 (load cell) to go into business, cause the people that understand this stuff are so few and far between. If anyone knows of a tuner within 100 miles of Kalamazoo, MI that can/will do this, I'm all ears. FYI, this is my setup:

'03 FLHRCI
95" HD Cylinders
95" HD Cast Flat Tops
AMS-ported stock heads, 85cc stock valve diameters
AMS Lifters
S&S/Andrews Gear Drive
TW37 G cams
Stock induction module
SE Air cleaner
Stock 2-2 head pipes w/ crossover
SE Performance Touring Mufflers

Til then, I guess close will have to do??
 
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