Jump to content

Boost cut or E-Throttle cut


Recommended Posts

So I took my car to the track today - 1/8 mile drag race.

First time out with a new turbo but I did have some street time on it. 1st pass right at 6400 rpm, 1st gear it fell on its face like ignition cut then it recovered and I shifted to 2nd, at 6400 rpm again same thing so I backed off a bit to about 80% throttle and finished the pass. 7.0 at 91 mph. Looked at the pc log and I hit 235 kpa at both instances of it cutting out. I though "oh that must by my set map limit" because I usually have everything set for 15-17 psi. Dial the WD duty down a smidge and run a pass at 10 psi without issues. 6.9 @ 102 mph. Ran 3 more passes at 13 psi without issue - 6.75 at 107.

I got home and looked at my map limit and its 240 kpa, not 235. Is it likely it hit early or is it more likely I had an e-throttle issue? I am using a GM LS7 gold blade TB that some have said gives issues with higher boost but I have been at 17 psi for a while now. Will the ecu store that as a code if it cut throttle due to tps vs aps disagreement? Would it have recovered that quickly? I thought it would limit the rpm until a key cycle. 

I may up the boost cut to 245 kpa to see if that fixes things or if it still happens at 235 kpa.

I did another log without saving that first one so I don't have it to upload unfortunately.

Link Extreme ecu in case that matters. 

Link to comment
Share on other sites

All limiters have a control range, for the MAP limit the default control range setting is 10Kpa.  That means if the limit is set at 240Kpa, it will start applying the minimum % cut (start cut) at 230Kpa, if MAP continues to increase then the %cut will increase up until the maximum "end cut" at 240Kpa.  You can turn on the advanced limiter settings if you want to adjust the control range, start cut or end cut from their default settings.  The larger you make the control range the smoother the limiting action will be but it will start to cut earlier.

Link to comment
Share on other sites

The regular LS3 gold blade ( which is probably same as what you're using ) works fine with boost. And the 90mm blade is quite adequate for up to around 2000hp....( and has been used beyond that )

So it shouldnt be too hard pressed at 6-7s 1/8ths.


But either way logging would show if the blade is not tracking pedal or your desired target.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...