Timing _ Gear Based ???

[Mad_Trbo]

I have seen over the years quite a few post mentioning that timing should be at ## number at the top of third gear or else? I believe I have even seen post mentioning timing adjustments at each shift point. The theory seemed to be if these adjustments weren't made knock would be induced.

Is there any particular reason this is the case?

I run the FAST XFI with MAP sensor and I am curious to know if this process is different with a MAP vs MAF system. Logic tells me it must be, if the advice mentioned above is only on a MAF system. I am thinking the engine doesn't necessarily care what gear the car is in or where in the RPM band it is. The MAP sensor tells the car ECM the load on the car and crank sensor computes RPM and based on such timing and fuel are dictated.

Am I in left field on this? As I evolve my understanding of tuning and get closer to my day on the engine dyno this will help me account for all possibilities.

 

[Mad_Trbo]

wrong place right timing

Am I posting this in the wrong place?

I think a discussion around timing events and the effects of timing would be invaluable to many of the users.

For those of you who have the knowledge please chip in, because I think a lot of us would like to know a lot more.

I know it has beenn discussed before but it never hurts to reinforce knowledge on topics such as .

Timing vs boost

timing and spool auto vs manual

timing and peak cylinder pressure where should you try to create this

are there any formula's for getting close with a start up map based on bore size position of spark plug quench etc...

I am not totally in the dark, but there are so many differing opinions it helps to hash them out and with each hash a better product evolves.

Thanks

 

[pacecarta]

at 6-7 am you're antsy cause no one replied ... come on at least wait till i get some coffee



heres a rundown

you tune to run as much timing as possible without KR and higher octane really dictates higher timing to its slower burn characteristics

1st gear loads the engine less due to gearing
2nd gear even more load placed due to gear change
3rd the endine sees even more load than 1-2 because o gearing

increased load will increase the potential for detonation , if your tuned timing on the edge at 1st then the load in the taller grears most likely will cause knock and 3rd gear and higher rpm is not where you want to see knock as bad things can happen fast
....so you either run lower timing in all gears/rpm or set up to pull a little out at the top for safety

got it

now how much is too much really you to find out through trial and error looking for best HP /MPH/ET as EVERY engine will be a little different and

fuel will affect the timing you should be expected to run

engine design ..ie. piston,heads ,cam, valves , gasket , milling which affect overall compression, boost -turbo efficiency - i/c size affecting charge air temp etc) will change the timing you can get away with

how close your balancer is to true 0 TDC will affect what number you program as some balancers can be off a few degrees (bhj balancers have been checked to be as much as 6* off)

if you want an octane based general timing look at fullthrottlespeeds site and their chips details
Octane (WOT spark advance degrees: low gear/high gear)
1 - 91 (17/15)
2 - 92 (18/16)
3 - 93 (19/17)
4 - 96 (21/19)
5 - 98 (23/21) <---- Translator Plus, Alcohol Injection
6 - 104(25/23)
7 - 108(27/25)
8 - 108+(29/27)

again those numbers are just numbers, your engine may repond differently

 

[Mad_Trbo]

Come on, I am just hungry to learn. Next time I'll remember nothing till after noon.

So a question, does this change based on the type of ECM you are running? Stock vs say XFI, only reason I ask is it seems the VE and spark tables take care of fuel and timing based on load with the XFI. Load which changes as you mention based on gearing. XFI looks it up and gives user defined spark and fueling.

What are the tables like on the stock computers? Is the map sensors only function on the stock cars for the boost guage? And with the MAF which I have never tuned on is there no way to measure load. Instead airflow and rpm and possibly speed are the measurement points? Speed and RPM tells the ECM what gear the car is in? TPS must be used too.

So if my assumptions are right with no way to measure load this is why stock tuners with chips care about the gear?

Just trying to make sense of it all.

 

[pacecarta]

if you want a rundown check gnttype.org they have a writeup for the breakdown of the stock BBKJ chip operations
http://www.gnttype.org/techarea/chips/chippage.html

Load is a calculated # which the stock ecm reads out as LV8 on a SM

at wot that #s is pretty much maxed out above15psi so thats not used to change timing once maxed stock ecm can use the 3-4 gear flags (in the 200r4 trans) to switch timing , or go based on speed input from vss (TT uses speedo if he is told speedo is accurate ) , as well as the PE mode calcs to switch from base timing to WOT timing


timing switches from base timing to WOT timing depending on TPS value and load calc when it goes to PE mode

on stock GN map is only to drive the indash gauge and in no way connects to ecm
for razors alky the map is be used for progressive to increase alky pump speed based on map output

turbo tweak std 5.6 chip uses maf and O2 sensor for cruising and idle fuel adjustment just as the stock chip but at WOT maf maxes at 255gm sec and that happens on most modded cars at 15psi or less , so what standard type chip does is base fuel off other once it gets maxed , like rpm , and speed based on a preset map table,
eric (TT) sets up the chips on a custom burn for each customers setup and the TT is nice in that its WOT operations for fuel and timing can be further tweaked by the user with wot fuel 1st gear fueling, 1-2 timing, 3-4 timing and all user adjustable

TT6.0 WB can do error correcting fueling at WOT based on a wideband sensor input with a user programmable AF target for PE 1-2 and 3-4 gears

tt 6.0 SD chips can actually run off a map (3bar) in a speed density format so no maf needed

chips like the bob bailey extender extreme are maf based fueled using a translator to drop the MAF output value by 1/2 or 1/3 allows the ecm to use maf values to control fueling up to 510 gm sec or even 765gm sec and timing is controlled with the translator
newer gen 2 translator works like a piggyback ecu and does even more adjusting of fuel and timing based on load and rpm

 

[Mad_Trbo]

Summation

Is it correct to assume then with my set up I have no need to worry about gear based timing?

The XFI's spark and VE table will adjust based on load which is driven based on the gear / throttle position and rpm.


Thanks by the way for walking me through this.

 

[Eric Stage I]

The XFI's spark and VE table will adjust based on load which is driven based on the gear / throttle position and rpm.

No, it only looks at MAP and RPM, has no comprehension of load once you get to full boost. At that point, the MAP reading is fixed at your boost level, so it never changes.

I wouldn't worry too much about whether you have gear based timing control if you're using race fuel in a track situation. The main reason for gear based control is so we can lower the timing in higher gears to prevent knock with "octane limited" cars, like street cars, or alky injection. If you're running C16, you don't "typically" have to worry about that.

 

[Mad_Trbo]

Clarity

Based on the last post this is still not clear to me, but thanks for the feed back to everyone.

I feel with the XFI's use of a MAP sensor the precautions used under the completely stock scenario become a non issue. That is with or without pump gas if the tune is correct at each load point. If it isn't then you have another problem all together.

 

[Eric Stage I]

What I'm saying is that once you reach full boost, say 20psi, the MAP reading will always be 20psi, no matter what gear or how much load there is.