1st Gen General Discussion The place for non-technical discussion about 1st Gen RX-7s or if there's no better place for your topic

GSL-SE stock ECU boost limit

Thread Tools
 
Search this Thread
 
Old Jul 4, 2017 | 07:56 AM
  #1  
Toybota's Avatar
Thread Starter
Can Post Only in New Member Section
 
Joined: Jan 2016
Posts: 1
Likes: 0
From: Oakville, Ontario
GSL-SE stock ECU boost limit

Hello everyone, My girlfriend and I are looking into supercharging her RX-7, now before you all comment "Turbos are better" I am aware, she wants to supercharge it for the drivability on the street. And she prefers the unmuffled exhaust sound that supercharging gives.

So, if we build a supercharger setup utilizing the factory EFI and factory port, how much boost can the stock ECU handle. Obviously were looking at a low number, 7-8 PSI is what the supercharger is able to do.

Obviously down the road we are going to get an aftermarket ECU put in and tuned for perfection, but for now, what can the ECU do?
Reply
Old Jul 4, 2017 | 08:01 AM
  #2  
peejay's Avatar
Old [Sch|F]ool
Tenured Member: 25 Years
Liked
Loved
Community Favorite
 
Joined: May 2001
Posts: 12,870
Likes: 574
From: Cleveland, Ohio, USA
The stock computer runs out of calibration at N/A power levels. IIRC the computer won't ever go over 70% duty cycle and you can easily exceed this capability with a stock block. (Which isn't saying much since you can't get much extra from a 6 port with porting - stock ports get you close to the limit of what you can do without going to extreme measures)

Naturally aspirated engines don't really care much since they can run WOT and lean of stoich just fine. Detonation is a non-issue.

Last edited by peejay; Jul 4, 2017 at 08:03 AM.
Reply
Old Jul 4, 2017 | 10:08 AM
  #3  
j9fd3s's Avatar
Moderator
Community Builder
Liked
Loved
Community Favorite
iTrader: (3)
 
Joined: Mar 2001
Posts: 31,837
Likes: 3,234
From: https://www2.mazda.com/en/100th/
i ran out of fuel in my GSL-SE with an exhaust and an FC block (larger ports).
Reply
Old Jul 4, 2017 | 10:43 AM
  #4  
insightful's Avatar
rotorhole
 
Joined: May 2017
Posts: 680
Likes: 70
From: retired rotorist
0?

the stock ecu isn't calibrated for boost, and any hacks you do to try and adjust timing or increase fuel appropriately are going to be extremely crappy.

you want to be cheap, then expect to blow it up real good and then pay later for your cheapness today. you'll need to upgrade the fuel system and i would suggest getting a standalone and reading up on how to tune, extensively.

7-8psi is plenty enough to get you into deep trouble with forced induction and detonation damage if you aren't doing things properly.

Last edited by insightful; Jul 4, 2017 at 10:46 AM.
Reply
Old Jul 4, 2017 | 11:10 AM
  #5  
KansasCityREPU's Avatar
Out In the Barn
Tenured Member: 20 Years
Liked
Loved
Community Favorite
iTrader: (9)
 
Joined: Mar 2005
Posts: 6,705
Likes: 1,250
From: KC
Cheaper to just get a S4 turbo and do a transplant.
Reply
Old Jul 4, 2017 | 12:28 PM
  #6  
Qingdao's Avatar
HeyHeyHey..Its the Goose
Tenured Member: 10 Years
Liked
Loved
Community Favorite
iTrader: (3)
 
Joined: Apr 2012
Posts: 3,056
Likes: 214
From: Charleston
Why not just buy a Camden supercharger?

Bolt on an go.
Reply
Old Jul 4, 2017 | 08:56 PM
  #7  
Jeff20B's Avatar
Lapping = Fapping
Tenured Member 15 Years
iTrader: (13)
 
Joined: Aug 2001
Posts: 15,725
Likes: 91
From: Near Seattle
And carb it!
Reply
Old Jul 5, 2017 | 05:59 PM
  #8  
DreamInRotary's Avatar
Always Wanting to Learn
Tenured Member 05 Years
iTrader: (49)
 
Joined: Aug 2011
Posts: 3,078
Likes: 42
From: Cambridge, Minnesota
Blowthrough carb would be cheaper and make more power in the end I'd expect. And that ECU can't even handle it's own stock power levels without any positive pressure.

Take KCREPU's advice and just go for an S4 TII swap, I've done it and it's an absolute riot to say the least
Reply
Old Jul 7, 2017 | 09:57 PM
  #9  
old_skool's Avatar
you know you want this
Tenured Member 15 Years
 
Joined: Dec 2005
Posts: 570
Likes: 9
From: inside
if you're set on supercharging, i'm probably pulling my camden next month. PM me if you might be interested in a deal.
Reply




All times are GMT -5. The time now is 09:08 AM.