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Old 05-08-2011, 07:25 PM   #1 (permalink)
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Relocating IAT sensor to improve hot starts

Has anyone relocated their Intake Air Temp Sensor from behind the throttle butterfly - were it can get heat soak - to the air cleaner? I have had a problem with kick back and vapour lock-up during hot starts with my bike since my 95 build. I have made it a lot better by removeing all primeing fuel with the TMax but would like it to be better. Wondering if moving the IAT sensor will do the trick.
Anyone tried it?

Rowdy

My bike: 2006 Softail
95 cu in
SE 10.25 HC Pistons with machined domes to get 9.8:1
0.030 HG
Andrews TW37G cams
Big Boyz Street ported Heads 86cc's
A Ness Big Sucker
V&H Big Radius 2:1
Thundermax with Auto Tune (INTIAL FUEL PULSE 0% CRANKING FUEL 6.3 msec)
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Old 05-08-2011, 07:37 PM   #2 (permalink)
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This has been tried and discussed on HTT. Steve Cole, the designer of TTS, says that it will NOT work out in the long run. The IAT needs to know the incoming fuels temp and NOT the outside temp while running... so you'd fix one thing, but screw up the rest.

Something isn't set right with the TMax is my guess.... seeing how your build looks fairly standard for a 95.

For the real deal on Tmax... go HERE and join up. There are a few TMax 'gurus' that really no sheit help folks.
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Old 05-08-2011, 09:22 PM   #3 (permalink)
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Thanks Wurk. Waiting to be approved by admin over at HTT so I can search around over there.
I don't see how the IAT in the air filter would give a false reading on incoming air temp....however on the other hand, I would think that heat would rise from an open intake valve on a hot, stopped motor and give a very high/false initial air temp reading which would affect the cranking fuel/timing maps.
If you bump the starter when the motor is hot, it will start straight up on the second hit. This makes me think that the initial bump draws hot air away from the IAT and it then gets a true reading of the air temp and adjusts accordingly. I have been searching the internet the last couple of nights about this and a lot of bikes and cars have the IAT sensor in the airbox from the factory, including the V-rod.
Zippers have an extension cable and air filter backing plates with provision to mount the IAT on their site but don't give any technical explanation/information about the benefits of doing it.

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Old 05-08-2011, 10:28 PM   #4 (permalink)
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You don't have something right. I have almost the same build with Tmax and it runs fine.
Call zippers and they will help you.
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Old 05-08-2011, 11:10 PM   #5 (permalink)
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Most cars no longer use Speed Density as the underlying tuning format like MOCO does.

The IAT CAN be off board when the system uses a MAF sensor.

Think of this... once bike starts? It runs fine? even with that heat soaked engine? THAT is because the IAT KNOWS it is heat soaked and adjusts accordingly.

There is some kind of setting in the TMax that ain't right is my guess... especially since you are running 37s and thousands of folks have no problem with 37s and EFI in general.

I'm into machine repair and diagnostics... the hardest thing for people to do is to NOT change wires around and to NOT alter the PROVEN design. The wires didn't magically switch scresw and the proven tech didn't become unproven overnight. With 1,000s of folks running TMax with normal IAT placement... I feel that can NOT be the issue...
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Old 05-09-2011, 12:20 AM   #6 (permalink)
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I had the same issue with my 95"/37g build. Replaced the starter with an All Balls and cleaned up the terminals and it fires right up no matter what conditions it faces.
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Old 05-10-2011, 06:30 PM   #7 (permalink)
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Quote:
Originally Posted by jasilva View Post
I had the same issue with my 95"/37g build. Replaced the starter with an All Balls and cleaned up the terminals and it fires right up no matter what conditions it faces.
Same here, except it wasn't an All Balls. 1.4kw though and I chased everything on the tuning side with no improvement.
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Old 05-10-2011, 08:07 PM   #8 (permalink)
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Are you running compression releases? What's your cranking compression? My 103 and current 124 build didn't and don't start well without the aid of the releases.
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Last edited by C-Cat; 05-10-2011 at 08:17 PM.
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Old 05-11-2011, 04:45 PM   #9 (permalink)
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If static CR is truly 9.8, cranking compression is just south of 190psi which is on the cusp of compression release territory. I install them when cranking compression gets over 185 because they extend battery and starter life and elminate heat soaked hot start kickbacks which can occur in south Texas summers. But there are plenty that run near 190 without releases with no serious issues.

Not a tuner but I sure wouldn't doubt Steve Cole. Not only the TTS designer but also designed the predecessor, the SERT. Calling Zippers is probably the best bet.
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Old 05-12-2011, 08:19 PM   #10 (permalink)
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Quote:
Originally Posted by Rowdy1 View Post
Has anyone relocated their Intake Air Temp Sensor from behind the throttle butterfly - were it can get heat soak - to the air cleaner? I have had a problem with kick back and vapour lock-up during hot starts with my bike since my 95 build. I have made it a lot better by removeing all primeing fuel with the TMax but would like it to be better. Wondering if moving the IAT sensor will do the trick.
Anyone tried it?

Rowdy

My bike: 2006 Softail
95 cu in
SE 10.25 HC Pistons with machined domes to get 9.8:1
0.030 HG
Andrews TW37G cams
Big Boyz Street ported Heads 86cc's
A Ness Big Sucker
V&H Big Radius 2:1
Thundermax with Auto Tune (INTIAL FUEL PULSE 0% CRANKING FUEL 6.3 msec)
Since you have tmax it has fuel pulse and cranking fuel. Iat has no effect on starting. I use to drop my timing to 0-1 degree in the 256 rpm area. This made the biggest difference on how it started.
Ron
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Old 05-13-2011, 04:43 PM   #11 (permalink)
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Zippers has the IAT relocation kit and thier backing plate that relocates it , if using the Tmax , call and verify what it will do for you with the TMAX
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Old 05-13-2011, 04:47 PM   #12 (permalink)
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One other thing all the new maps that came out about week ago have the timing in the 256 and 512 at 0 , changed timing on friends roadking and it made alot of diff on the starting much easier he does not have compression releases. also make sure your iac home is correct if its two high the bike will have a high idle for a second after start then come down , lower the number by 5 if this is true and do the 30 second on and off 3 times then try start again, if the iac to high can cause hard starts .

check the changes they did on the new maps most are modified versions of the existing maps with timing changes and idle stuff ,
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2001 FLSTFI
116" 11.3 comp
TW9BG + 4 cam
RR vented cam plate
Zippers billet heads
HPI 53 mm TB
6.2 gps
Boarzilla - from 05 dyna
4" Primal belt drive 3.23 gearing
bandit clutch
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Old 05-15-2011, 06:11 PM   #13 (permalink)
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CCP is right on 185 psi and I don't have compression releases.
I did alter the map quite awhile ago to pull all the timing in the 0, 256 and 512 maps, and also reduced it in the the 768 map with no noticeable inprovement.
I have played around with the initial fuel pulse settings and found that if I cut all fuel pulse out the bike would take an extra couple of revolutions to start but wouldn't get the compression lock and kickback.
Just got an email back from Zippers and they recommend trying the new revised maps, so I'll give that a bash.

Rowdy
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Old 05-16-2011, 02:18 PM   #14 (permalink)
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Id try either cranking compression or possibly differant cam to bleed off little of the cranking compression. I have a 114 ci all bore running 11.2:1 and about 195 cc and most of the time don't need the compression releases but when it get stuborn they make world of differance. Ive been thinking about the s&s cams with the compression release system in them just not sure I trust cams with moving parts in them to take a real beating.
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