LS3 Sidedraft ITB in a C5 (Gen 3 PCM)

Printable View

11-07-2019
nsogiba

LS3 Sidedraft ITB in a C5 (Gen 3 PCM)

Looking to see if anyone has experience tuning an ITB setup like this:

https://speedmaster79.com/Chevy-GM-L...Complete-Satin

This would be going on a 2000 C5, LS3/L92 6.2L, SBE and stock heads (no porting) with a BTR LS3 Stage 2 cam (Specs: 225/238 .612"/.585" 113+3). T56 and 4.10s. Intended use is a weekend warrior with a bunch of casual road racing use in the warm months. I am not too concerned with overall power gains, more so interested in the increased driveability and mostly the sound!

I?m thinking about adapting an LS1 78mm or LS2 silver blade throttle body, remotely mounted, to act as a servo with custom linkage to actuate the 8x throttle bodies mechanically, so theoretically DBW vs DBC is not really a concern. Since the car is currently running the Gen 4 motor it's using a silver blade LS2 TB with an conversion harness, but no reason it can't use an LS1 TB either.

Concerns:

-Need to figure out motion ratio of DBW TB vs ITB linkage to make sure they?re 1:1. Although the TPS% and actual DBW blade position is not the same, I'd think that keeping the ITBs and the "servo" (TB) would make sense.

-Need to fab up a vacuum manifold to supply vacuum to MAP, brake booster, HVAC system, and maybe a port for IAT. I'd need to tap a fitting into each runner between the throttle blade and the head, then join them at a common log mounted to the valley...

-PCV ? can add a port on this vacuum manifold to plumb similar to an OEM setup ? or just run lines from the valve covers to a vented catch can.

-Filtration ? I only drive my car on nice weather days, so elements aren?t a concern but there is still the issue of general dust/debris/leaves/etc. Filters/screens look goofy and rob power

-Tuning - The biggest concern. Obviously MAF is going bye bye and I will have to convert to Speed Density, but have read that the ITB setup causes the MAP to read atmospheric (100kPa) over 20-30%, which basically renders it useless. Does HPTuners support Alpha N calculations (RPM vs TPS only)?

What other special considerations do I need to look at when using HPTuners to calibrate an ITB setup?
11-12-2019
cobaltssoverbooster

1) im pretty sure you can disable the DBW function and run standard DBC by setting the System Option for ETC to 0. (little out of practice on the DBW to DBC conversion, just verify this with others before taking it as 100% possible)
2)You'll need something more than a vacuum log. It will only benefit you to have a vacuum canister of some sort to help dampen the pulse between cylinders. Typically i see too much map signal fluctuation with just something like a blank fuel rail tapped for 8 runner ports and a map sensor.
3)vent to atmosphere if you can, otherwise run a hose to one of the trumpets. A catch can is easy to install inline and prevent one runner from gathering oil and being "different" from the other 7 runners. If you have a common filter housing for each bank then route pcv into the filter housing of one or both banks away from the trumpets.
4)You can install trump screens or fabricate a custom filter housing for each side. The trumpet screens do restrict flow more than the custom housing will but it will show the ITB setup off more. Becomes a user preference trade-off.
5)You can disable the maf sensor and run straight SD no problem. As long as you run the log to canister setup mentioned in 2&3 then your map signal shouldnt create too much headache.

I have done this to multiple Porsche 928's, a 914-6, standalone efi setups for SBC and BBC, and one SBF application. Using a GM ecu and modifying the mechanical components to provide an accurate signal source should allow you to tune just like any other factory car with no MAF.
11-13-2019
david_viny

There is also a 1 Bar speed density upgrade for some (all?) gen 3 PCMs. This gives you a rpm vs tps adder table to the VE table. That is basiclly gives you a blend of alpha n and SD which id assume would be great for ITB's.
11-13-2019
nsogiba

Quote:

Originally Posted by cobaltssoverbooster

1) im pretty sure you can disable the DBW function and run standard DBC by setting the System Option for ETC to 0. (little out of practice on the DBW to DBC conversion, just verify this with others before taking it as 100% possible)
2)You'll need something more than a vacuum log. It will only benefit you to have a vacuum canister of some sort to help dampen the pulse between cylinders. Typically i see too much map signal fluctuation with just something like a blank fuel rail tapped for 8 runner ports and a map sensor.
3)vent to atmosphere if you can, otherwise run a hose to one of the trumpets. A catch can is easy to install inline and prevent one runner from gathering oil and being "different" from the other 7 runners. If you have a common filter housing for each bank then route pcv into the filter housing of one or both banks away from the trumpets.
4)You can install trump screens or fabricate a custom filter housing for each side. The trumpet screens do restrict flow more than the custom housing will but it will show the ITB setup off more. Becomes a user preference trade-off.
5)You can disable the maf sensor and run straight SD no problem. As long as you run the log to canister setup mentioned in 2&3 then your map signal shouldnt create too much headache.

I have done this to multiple Porsche 928's, a 914-6, standalone efi setups for SBC and BBC, and one SBF application. Using a GM ecu and modifying the mechanical components to provide an accurate signal source should allow you to tune just like any other factory car with no MAF.

I was under the impression that a DBW PCM could not support a DBC application due to the fact that it doesn’t have the IAC driver to control the IAC valve. That’s why I want to stick with the DBW.

A large vacuum canister is not a big deal, that’s just additional fabrication.

Tuning on the DBW PCM is my biggest concern, as I hear the MAP signal shoots to 100kpa (atmospheric) at anything larger than a small throttle input and can’t provide additional fueling via VE table. I am reading that one way to get around this is a TPS multiplier in the cells where the MAP drops out.

Quote:

Originally Posted by david_viny

There is also a 1 Bar speed density upgrade for some (all?) gen 3 PCMs. This gives you a rpm vs tps adder table to the VE table. That is basiclly gives you a blend of alpha n and SD which id assume would be great for ITB's.

Thanks for the tip! I wonder if there is some tutorial or example on that. I'll do some digging tonight.
01-03-2020
55chev

Quote:

Originally Posted by cobaltssoverbooster

1) im pretty sure you can disable the DBW function and run standard DBC by setting the System Option for ETC to 0. (little out of practice on the DBW to DBC conversion, just verify this with others before taking it as 100% possible)
2)You'll need something more than a vacuum log. It will only benefit you to have a vacuum canister of some sort to help dampen the pulse between cylinders. Typically i see too much map signal fluctuation with just something like a blank fuel rail tapped for 8 runner ports and a map sensor.
3)vent to atmosphere if you can, otherwise run a hose to one of the trumpets. A catch can is easy to install inline and prevent one runner from gathering oil and being "different" from the other 7 runners. If you have a common filter housing for each bank then route pcv into the filter housing of one or both banks away from the trumpets.
4)You can install trump screens or fabricate a custom filter housing for each side. The trumpet screens do restrict flow more than the custom housing will but it will show the ITB setup off more. Becomes a user preference trade-off.
5)You can disable the maf sensor and run straight SD no problem. As long as you run the log to canister setup mentioned in 2&3 then your map signal shouldnt create too much headache.

I have done this to multiple Porsche 928's, a 914-6, standalone efi setups for SBC and BBC, and one SBF application. Using a GM ecu and modifying the mechanical components to provide an accurate signal source should allow you to tune just like any other factory car with no MAF.

Thanks for the info. :)
01-03-2020
1970ss8.1

I don?t think the DBW motor will be able to handle the added stress of all the moving parts. You should go DBC. To do that,You have to cross reference the ECU number with the DBC ones. I?m doing a DBC conversation right now. My ECU was DBW but had the IAC drivers in it. I couldn?t get it to work. I had to change the operating system. With a OS from a DBW vehicle won?t drive the IAC. I ended up getting a 2004 GTO ECU and writing a GTO OS in it then copy over the tables from my 8.1. Now the IAC and tps works. If you have a ECU that is on the list from here https://www.mrk-motorsports.com/gm-iac-pcms/
You can just write entire a OS from a DBC vehicle and it will drive the IAC. Simply changing the ETC to 0 in the system options doesn?t work. I have a few O/S s saved that are DBC if you need one. Are you using a P01 or a P59. This applies to the P59. The P01 should have the IAC drivers already and I have a DBC OS for that as well.