Big bore afm

Big bore afm

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Discussion

jojackson4

Original Poster:

3,026 posts

136 months

Tuesday 25th October 2016
quotequote all
It's that time of year when I start thinking about daft stuff this is the first one
Can you bore the OE afm to open it up abit?
As it's the main bottle neck before it hits the inlet manifold if I can be done how far can you go
Thanks Peter

N7GTX

7,823 posts

142 months

Tuesday 25th October 2016
quotequote all
My understanding is that the element (the sensor) is matched to the housing to give the most accurate results. By altering the bore i.e. making it larger would mean the air flow over the element will change and so the ECU will get the wrong signal.
There are many element replacements for AFMs but reading the Bosch technical stuff it is forbidden on their products to change the element on its own.


QBee

20,904 posts

143 months

Wednesday 26th October 2016
quotequote all
You can use a 20AM AFM, they are not expensive in themselves, but you will need a remap at Chesterfield.

jojackson4

Original Poster:

3,026 posts

136 months

Wednesday 26th October 2016
quotequote all
Thanks gents
The remapping bit is the one I am trying to avoid

QBee

20,904 posts

143 months

Wednesday 26th October 2016
quotequote all
Jools, at Chesterfield, doesn't generally charge a lot, and it's actually not a bad idea to check from time to time that your fuelling across the rev range is spot on, especially if you give it full beans on occasion..
You don't want to be unwittingly running lean at higher revs, for example.....

Give him a call - 07521 288875. Mention my name if you like.
Talk over what you are trying to achieve - he is very knowledgable.

blitzracing

6,387 posts

219 months

Wednesday 26th October 2016
quotequote all
You can bore out the 5AM but it opens a whole can of worms. The reduced airflow velocity reduces the voltage output, so the unit goes out of calibration. I did go to the effort of making a box of electronics to boost the signal back to the correct level for any given airflow, but that then cant take into account the extra volume of air you can now get through the AFM, as the fuel map is still calibrated for the peak airflow as it was, not what it is now. This means you dont get the extra required fuel to go with the extra air. You certainly could bore the unit out, and then remap against the new voltage range, and a few mm in diameter makes quite a big difference in peak airflow, but TBH you are better off with a 20AM or Bosch. The 20 AM is better because its voltage response is far nearer the 5AM, simply about 10-15% lower for any given airflow, so you have decent headroom for accurate mapping near peak airflow. The problem is the 20 AM is not available new any more- all the ones on Ebay are nasty Chinese knock offs with poor voltage response, but there are a few on the second hand market.

gmw9666

2,734 posts

199 months

Wednesday 26th October 2016
quotequote all
If it helps

Last year I had Joolz do an ecu upgrade / map / RR session on my old 430 Chim, car was great after and a big thumbs up for kits and classics

For fun we tried the larger AFM and did back to back tests. Didn't provide any upgrade in bhp

We also removed the elbow and did a straight pipe into the plenum (vs ribbed elbow) again just for fun and you know what, no change

So from my chair, smooth bore elbows and larger afm's = zippo

Hope that helps :-)


CHIMV8 500

2,768 posts

220 months

Wednesday 26th October 2016
quotequote all
gmw9666 said:
If it helps

Last year I had Joolz do an ecu upgrade / map / RR session on my old 430 Chim, car was great after and a big thumbs up for kits and classics

For fun we tried the larger AFM and did back to back tests. Didn't provide any upgrade in bhp

We also removed the elbow and did a straight pipe into the plenum (vs ribbed elbow) again just for fun and you know what, no change

So from my chair, smooth bore elbows and larger afm's = zippo

Hope that helps :-)
Had a chat with Jools on yours, and its the first time he has ever had a negative with installing the 20am.

CHIMV8 500

2,768 posts

220 months

Wednesday 26th October 2016
quotequote all
QBee said:
Jools, at Chesterfield, doesn't generally charge a lot, and it's actually not a bad idea to check from time to time that your fuelling across the rev range is spot on, especially if you give it full beans on occasion..
You don't want to be unwittingly running lean at higher revs, for example.....

Give him a call - 07521 288875. Mention my name if you like.
Talk over what you are trying to achieve - he is very knowledgable.
Im in the queue,when i can sort a day out to Chesters

Andav469

957 posts

136 months

Wednesday 26th October 2016
quotequote all
gmw9666 said:
If it helps

Last year I had Joolz do an ecu upgrade / map / RR session on my old 430 Chim, car was great after and a big thumbs up for kits and classics

For fun we tried the larger AFM and did back to back tests. Didn't provide any upgrade in bhp

We also removed the elbow and did a straight pipe into the plenum (vs ribbed elbow) again just for fun and you know what, no change

So from my chair, smooth bore elbows and larger afm's = zippo

Hope that helps :-)
I had my 500 up to Joolz 18 months ago for a remap and 20am AFM, not only did it give more power, but removed most of the shunting and cold start issues, I can now start it up and drive smoothly away immediately.



gmw9666

2,734 posts

199 months

Wednesday 26th October 2016
quotequote all
CHIMV8 500 said:
Had a chat with Jools on yours, and its the first time he has ever had a negative with installing the 20am.
https://www.youtube.com/watch?v=kt3B8HKeEMw

jojackson4

Original Poster:

3,026 posts

136 months

Thursday 27th October 2016
quotequote all
Thanks for the replying gents I will stick to the 72 mm plenom

OleVix

1,438 posts

147 months

Thursday 27th October 2016
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I have a used 20AM from jools, used 1 year. You can have it for half price. + shipping

jojackson4

Original Poster:

3,026 posts

136 months

Friday 28th October 2016
quotequote all
YHM