5 Minute Turbo Tech Tips with Reed, Episode 1: Ignition Timing and Backpressure

In this episode I will go over the importance of proper ignition timing on a turbocharged application and how it can effect the backpressure (drive pressure) in your system. Have a specific topic you would like me to cover? Drop it in the comments below and I will do my best to make it happen!

[@mattmorrison6958]

Really good info and nuance here, will be checking out more and subscribed! Much appreciated

[@workturbo]

Thank you Matt!

[@raymondguzman1907]

Good info thank you

[@kylemilligan752]

Gotta be real careful with high backpressure combos. They love ignition timing because of the egr effect, you gotta know when to stop

[@hardhead7056]

This advice could help in the diesel world. I think im having the same issues. High Egt. Drive.

[@wanderingquestions7501]

Nice shop

[@workturbo]

Thanks! We try to keep it "nice!"

[@finnroen2334]

There seems to be a lot of really bad tuners around just punching numbers on a keyboard not analyzing anything other than HP peak number. Bergen StreetRacing Team have "invented" something they call "The theoretical NA engines performance." Examples can be seen if one google " Den teoretiske sugemotoren ." photos. After a dynopull they divide the torque number and hp number with the MAP number at the all the different RPMs. (This should really be in the dyno software.) Doing this, one will find that "The theoretical Na Engines performance" will be pretty stable before it starts to goes south and and EGT goes way north. How far beyond the peak NA result one wants to push the tune and the engine differs vastly. Very interessing using this knowlage when whatcing big names in the industry on the dyno, incl. Fueltech, Murder Nova, Nelson, Shane T etc. comes to mind. :)

[@workturbo]

I love this...we always have used some type of "average power number"...some call it by different names, and some arrive at it more scientifically then me...but always taking the average HP and average torque...and averaging that seems to be the way to go! I try to evaluate that in a real world "range" depending on application. Obviously a street car will be slightly different than a drag car, pulling class or over the road truck...but once you define the prime operating range and focus your gains there...it gets nothing but better! -Reed

[@FadetoBlack1463]

Reed would advancing the camshaft 2.5 degrees show an increase in boost pressure with all other things being equal?

[@workturbo]

I guess it would really come down to the current camshaft in the engine. I dyno'd a DOHC 4 cylinder extensively and we did nothing but move the cam CL for a bunch of tests. On that engine it made a bit more boost earlier when we advanced the intake and retarded the exhaust, but it cost us RPM range. Most modern turbocharger cam grinds are going to have a much more aggressive advanced EVO and the intake event seems to start in a more traditional or even retarded IVO position. Mainly due to the nature of higher boost pressures, compression ratio and more advanced turbine designs that flow. Really did not answer your question, I know...but without knowing all of the details it is hard to say. My generic answer for a "turbo" cam that it mild in a single cam (V8/6, and SOHC engines) the answer may be "yes". I had a traditional SBC years ago that had a simple 236/236 @.050 cam, 110 LSA. We replaced it with the same lobe design, but different LSA. Let me see if I can find that data, we may have played with cam timing on both, but I cannot remember (that was 1997!)

[@FadetoBlack1463]

@@workturbo This cam is a 252 256 @.050 115 lobe sep, .750 total lift. 403 cu GT55 91mm cast wheel Garrett BB. I advanced the cam 2.5* and with very similar DA and the same dome pressure it appears to have picked up 1.5 psi boost reading from the intake manifold. Spool up has improved as expected, but wouldnt that increase in boost show as less air flow?

[@nesmio7378]

6:08 You say in the sentence that you had a 1.75 boost to drive pressure ratio, surely you mean drive pressure to boost ratio? 1.75 drive pressure for every 1 boost pressure? What is the maximum ratio you can accept?

[@workturbo]

Thank you for the correction...doing "1 take videos" has its drawbacks. You are spot on, 1.75:1 EMAP to MAP. The maximum drive pressure tolerated will be different for every engine. The major components that influence this number the most will be: camshaft, cylinder head, header primary, header collector, wastegate placement, turbine a/r and turbine wheel. Tuning issues we see that falsely make this number larger are: Less than optimal ignition timing, injector phasing, incorrect injector sizing (late end of injection cycle) and lastly utilizing the incorrect fuel for the tune (tuned on one fuel and raced on another without thought put into the characteristics of the fuel). Always take into consideration intercooler pressure drop, air restriction in the inlet and exhaust as well. Ramble over, thank you!

[@teagreen2220]

Doing conversion from NA to turbo with my stock ECM I noticed that the timing cannot easily be increased on the timing table because it only goes to 1.2 grams per cylinder of air then it carries the timing set on the last line all the time during higher values. I use a electronic control I made to send the ecu false IAT temps so that it references the IAT table and pulls timing while boost increases. This way I can actually control the timing for any boost pressures. I think most people when adding a turbo to a stock setup will run into these problems. Too bad haltec systems are so expensive…

[@workturbo]

We have "fooled" the ECU many times this way...and there are many aftermarket "boxes" that do the same thing (Apex'i Super Afc, LINK and others from back in the "day"). Works well to a point. Haltch Elite 550's are less than 1k, Microsquirts are less than $500.00...very affordable and suit most installations. I have used the microsquirt on at least 3 builds in the last 4 years, awesome power for the money.

[@lukedougherty7078]

baseline camshaft timing would throw this all out of whack as well I guess play with it see what you come up with

[@workturbo]

Cam timing obviously plays a huge role! I am slowly compiling data for an upcoming video later this summer (hopefully) going over one of our dyno engines that the only changes made were to the exhaust opening event (EVO BBDC) and the subsequent change to the engines performance. Reed

[@802Garage]

Can you explain why this is? I think it will be confused to most amateur tuners like me. I'm guessing it's because advancing the timing was giving a more complete burn in the cylinder and therefore less leftover air fuel mixture being burned in the exhaust?

[@workturbo]

In short, you are correct. If you have the data logging capability, It can be seen quite easily. Run the engine at a moderate load and move around the timing from optimal to "late". You will notice EGT will rise, drive pressure will go up, the boost may start to increase unless the wastegate does not catch it quickly. Same can also be said for the injector phase angle... Now, a bit of a disclaimer. Depending on how the engine is set up...camshaft, hp etc, this may not be easy to see. The cars I am working with are generally operating in the 90-100% capacity of the turbo system. The one I have with the most data is a 427" Energy SBF with twin 88mm turbos set up to run LDR/ODR, running on gasoline...but we have seen the same results time and time again on simpler setups. One day when I actually have the man power to record some tuning videos, I will upload them. Most of the time we are a 2-3 person team at the races and video content for youtube falls way down to the bottom of the priority list.

[@802Garage]

@@workturbo Awesome thank you!