Sale ends todayGet 30% off any course (excluding packages)

Ends in --- --- ---

Turbo sizing for compound boost

Webinar Questions

Forum Posts



Tech Articles

Ask questions about webinar lessons here. To see the Previous Webinars for a complete list of archives tuning webinars. 

= Resolved threads


Just finished watching a webinar about using the Borg Matchbot but not sure exactly how to use it for a compound turbo into blower setup. I'll do my absolute best to keep it short and to the point for such a complicated setup.

History: For the past 10+ years I've been running a stock K24a2 with a highly modified JRSC M62 blower spinning to 20,400 blower rpm peak on 91/e10 crap pump gas and 2800cc/min of water (20%)/meth (80%) injection through the blower making 425whp and 336wtq. The water meth being the only source of octane boosting and charge cooling with peak IAT's post blower being ambient to sub ambient. Using IAT sensor and lean protection for fail safes in case of WM failure. Using this setup I've experimented with pushing Ign way past MBT with no knock as well as having accidentally ran WOT at full boost leaner than the wideband can read with zero damage or knock due to the amount of water meth being used. Also control supercharger bypass with a solenoid for boost by gear.

Goal: A well rounded do it all setup mostly for weekend street driving with occasional track use. Power between 300 - 1025whp with the turn of a knob. Would like to make as little power as possible for canyon type roads and typical street driving and as much as 1000+ whp for highway/track and anywhere in between. I'm certain I want to retain the supercharger for instant throttle and boost response. Turbo "lag" is unacceptable.


Engine & Chassis: Fully built SFWD K24 engine swapped into my 91 NSX.

Power: JRSC M62 supercharger @ 17,600 blower rpm peak + EFR 9280 w/ Tial V-band 1.3AR

WG: TurboSmart Electronic straight gate

Fuel & Cooling: E85 (flex fuel) + Water Meth

TB: Bosch Motorsport DBW 82mm

ECU: Nexus R5

Safety Plan for WM: Lean protection + IAT ign compensation + EGT's

Details: Turbo will directly feed blower which directly feeds engine with no other cooling other than water meth which I've proven can work. In testing if this becomes an issue I can work out more traditional intercooling later. I plan on using the E-gate with priority placement and hope to have absolute control over power delivery. I can also experiment with controlling the supercharger bypass to see if opening it at a given point results in more power or lower IAT's.

Concerns: What little information is out there says to go with as large a turbo as possible especially in regards to turbine and AR. When attempting to use matchbot most of the data points are to the left of the compressor map. I'm not sure if running so far to the left can damage the turbo since I believe all I should care about is the upper rpm being close to the island for this application. However the matchbot may be irrelevant with the information I've entered since I don't know how to account for the supercharger or lack of an intercooler while still having cooling.

Any and all input regarding anything mentioned is greatly appreciated!

If you haven't done so, I'd STRONGLY recommend checking out Mr Gale Bank's channel* - https://www.youtube.com/c/bankspower ,with these being the main sub-channels - https://www.youtube.com/watch?v=hbsnzC3nXOU&list=PLwtmrqcWzLtRdv9XAlV1l7NBnQfGU1mi1 https://www.youtube.com/watch?v=iBoyW2e0ra0&list=PLwtmrqcWzLtQsQGxE-x2i8GaPgEuItUkn and https://www.youtube.com/watch?v=Cjnl67QI6nU&list=PLwtmrqcWzLtRXpEFXeXa3YF-L0xSK2Ml2 At the very least, they should give you a lot of food for thought!

While he is primarily a diesel guy, he has done a LOT of work on different charging variations of engines, with full logging and explanations as he goes along on what's happening, and why. All the basic principles can be directly applied to petrol/gasoline engines where he was also one of the pioneers with turbo's on street engines.

I would point out a couple of potential problems, though - superchargers are designed to work with ambient air pressure and ambient temperature at the intake. This means high(er) boost levels can cause seal failures from the changed pressure deltas and/or seizures if the thermal expansion isn't accounted for. At a minimum, I'd suggest having a talk to the tech' guys at the supercharger company - they may be able to offer suggestions.

In the meantime, it seems like you could spend some useful time working on the tune for what you have, as it seems you're still leaving a lot on the table if you can have those issues without any actual problems.

*Not just you, but ANYBODY who has ANY interest in forced induction.

I've definitely watched several of his videos!

As far as the blower reliability I'm uncertain. It seems that the few people running a setup like this don't seem to be having issues but I remain curious on this.

I've even considered simplifying the setup by possibly adding 2 fuel injectors pre blower that I can control as secondary injection that come on with boost and ramp up as pressure increases and map that out like normal instead of or in addition to water meth injection.

Still not sure on ideal turbo sizing or if the 9280 is the way to go.