New 75mm Throttle Body

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Craig Smith
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New 75mm Throttle Body

Post by Craig Smith »

Got a new BBK 75mm TB in today for the 91 5.0
I also bought the spacer to delete the EGR.
I have heard that I will need to change the idle set up a bit but that the ECM should compensate for the larger TB all by it's self.
Question is, should I go back the the original tune for the adaptive learning process to work or will it take care of it in just driving the car?
1986 Jauguar XJ6 with a transplanted 95 LT1, 1990 5.0 LX Mustang, MSD6AL, MSD Blaster coil, Shorty headers, no cats, h pipe, flow masters, Edlebrock Performer intake and plenum, Aeroquip pressure regulator.
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dex
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Post by dex »

You will need to change the 'Throttle Body Air Flow' (aka ITHBMA) parameter because the flow characteristics of the throttle body have changed. This value is used by the eec to determine the ISC dutycycle required to meet the calculated desired idle air flow.

You'll probably also need to tweak the acceleration enrichment items slightly too.
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Craig Smith
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Post by Craig Smith »

Found the enrichment table.
No go on the other one
How much do you think I need to go Up/Down on the tables?

Someone said I should just install it, check the TPS set up and then disconnect the battery and let the adaptive fix it.

That sounds a little too easy to me
1986 Jauguar XJ6 with a transplanted 95 LT1, 1990 5.0 LX Mustang, MSD6AL, MSD Blaster coil, Shorty headers, no cats, h pipe, flow masters, Edlebrock Performer intake and plenum, Aeroquip pressure regulator.
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dex
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Post by dex »

For the acceleration adjustment what you are trying to do is deal with the different tip in air flow characteristics of the new throttle body. If I was you, I would try to get away with just using the ‘Accel Enrichment Multiplier vs TP’ (aka FN331B) table first. I don’t know of any hard and fast rules and without using a wideband lambda sensor to spot any lean tip ins you are going to have to rely on ‘feel’ to make any adjustments.

Regarding the 'Throttle Body Air Flow', here’s a a guide of what to do;

With the engine fully warmed up and the idle steady, disconnect the ISC and hopefully the car will still be idling. Adjust the throttle body stop screw so that the car will just barely idle and set the TPS to ~0.95 volts.

Because you don’t have real-time datalogging you will have to measure the MAF’s voltage at idle. Take several readings over a period of time to get a typical average (a bit trial and error but eventually you’ll get a reasonable figure). I suggest you measure it at the eec to take into account any resistance in the loom. You then need to compare this value against the MAF transfer curve to deduce the airmass at idle. Convert the kg/hr value into lb/min and input this value into the 'Throttle Body Air Flow' parameter.

Your MAF curve has to be accurate for this to work.
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Craig Smith
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Post by Craig Smith »

Well,
Got my work load now.
The MAF settings on the car have not been touched. It's bone stock
Let me get everything hooked up and I'll give the list a holler for trouble spots.
Oh,
I also got the EGR Delete plate.
I was expecting it to be a bit wider than the one I got.
It's about 3/4" wide. the EGR is a good 1.5".
Hope I have room for the linkage

Thanks again Dex for the reply. your a big help
1986 Jauguar XJ6 with a transplanted 95 LT1, 1990 5.0 LX Mustang, MSD6AL, MSD Blaster coil, Shorty headers, no cats, h pipe, flow masters, Edlebrock Performer intake and plenum, Aeroquip pressure regulator.
User avatar
Craig Smith
Posts: 67
Joined: Mon Oct 23, 2006 5:22 am
Location: Mauldin, SC
Contact:

Post by Craig Smith »

Installed the 75mm TB last night.
Had a major distance problem with the linkage.
EGR delete plate that holds the throttle linkage is way too close and hits the hard line coolant tube.
Installed it with the old EGR plate and hooked everything up.
Reconnected the battery, fired it right up!
Good idle.
Went for a drive to check it out, other than a need for a auto tranny TV cable adjustment car ran well.
I sort of noticed a differnt engine "tone"?
I may be full of it on that one, my son said I can't hear well anyway so he said he didn't notice anything.
I had a bung welded in the passenger side pipe yesterday to hold the sensor for the LM-1
I hope to make a data log today to see what we have going on inside all the whirling stuff.

I'll post the results.
1986 Jauguar XJ6 with a transplanted 95 LT1, 1990 5.0 LX Mustang, MSD6AL, MSD Blaster coil, Shorty headers, no cats, h pipe, flow masters, Edlebrock Performer intake and plenum, Aeroquip pressure regulator.
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