tip/map ratio effects on fuel demand

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rac
Posts: 45
Joined: Tue Aug 14, 2018 6:06 am

tip/map ratio effects on fuel demand

Post by rac »

I've just installed an emap sensor and I am looking at how to integrate emap/imap (or tip/map) ratio to make a more robust fuel table for VE fluctuations caused by the pressure differential across the cylinder and hopefully improve accuracy at part throttle variation, WG operation etc. I could do this partially with TPS but I believe tip/map is a more direct measurement of what I am wanting to account for.

From another thread I found this comment:
RICE RACING wrote: Thu Aug 09, 2018 1:29 am You do need to know what your engine type looses in terms of air flow when the pressure differential across the engine changes (its not the text book function sadly) but its not too hard to work out either.
I feel like I have gone around in circles a bit trying to analyse my data, the best fit I have come up with so far appears to be:

TIP/MAP Multiplier = 1/(0.485*(tip/map - 1) + 1)

With the 0.485 coming about from iteration of logged data in a spreadsheet for best match to create a flat(ter) base fuel table.
i.e. VE is not affected in a 1:1 manner to tip/map ratio, however it does appear to be significantly affected.

Anyone care to comment on the validity of the above or otherwise an example tip/map multiplier to see if I am on the right path?
I don’t want to fall into the trap of data fitting for the sake of it despite the execution being flawed.
rac
Posts: 45
Joined: Tue Aug 14, 2018 6:06 am

Re: tip/map ratio effects on fuel demand

Post by rac »

Dont worry about the above post, I realised I made a stupid omission in the data I had by not accounting for cam timing.

If I feel the urge I might gather and sort data into rpm brackets with stable valve timing events and then try and look for this relationship;
VE = A + B*(IMAP/EMAP), where A and B are constants empirically derived.
drewbinsky
Posts: 8
Joined: Tue Jun 13, 2023 8:18 am

Re: tip/map ratio effects on fuel demand

Post by drewbinsky »

It's difficult to give a conclusive judgment of the correctness of the formula or offer an example without more information or specific statistics about your engine. multiplier for TIP/MAP blossom word game
lesary
Posts: 5
Joined: Wed Mar 08, 2023 7:33 am

Re: tip/map ratio effects on fuel demand

Post by lesary »

It's difficult to give a conclusive judgment of the correctness of the formula or offer an example without more information or specific statistics about your enginegeometry dash subzero multiplier for TIP/MAP
Where are you having trouble adding information or numbers?
drewbinsky
Posts: 8
Joined: Tue Jun 13, 2023 8:18 am

Re: tip/map ratio effects on fuel demand

Post by drewbinsky »

rac wrote: Fri Jul 08, 2022 1:22 am Dont worry about the above post, I realised I made a stupid omission in the data I had by not accounting for cam timing.
heic to jpg
If I feel the urge I might gather and sort data into rpm brackets with stable valve timing events and then try and look for this relationship;
VE = A + B*(IMAP/EMAP), where A and B are constants empirically derived.
This can indeed be a helpful approach to make your fueling more precise under various engine operating conditions
legendsmug
Posts: 2
Joined: Wed Dec 20, 2023 12:57 pm

Re: tip/map ratio effects on fuel demand

Post by legendsmug »

rac wrote: Fri Jul 08, 2022 1:22 am Dont worry about the above post, I realised I made a stupid omission in the data I had by not accounting for cam timing.

If I feel the urge I might gather and sort data into rpm brackets with stable valve timing events and then try and look for this relationship;
VE = A + B*(IMAP/EMAP) basket random where A and B are constants empirically derived.
I'm having a difficult time showing that this formula is correct.
stevieturbo
Posts: 1321
Joined: Sun Dec 07, 2008 2:04 pm

Re: tip/map ratio effects on fuel demand

Post by stevieturbo »

I'm having a difficult time with the amount of F'ing spambots on forums these days.
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