1600F EGT's too high during high speed cruising? - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


DIY Turbo Discussion greddy on a 1.8? homebrew kit?

Reply
 
 
 
LinkBack Thread Tools
Old 08-26-2010, 10:38 AM   #1
Junior Member
Thread Starter
 
Join Date: Oct 2007
Location: Staten Island, NY
Posts: 159
Total Cats: 0
Default 1600F EGT's too high during high speed cruising?

Pretty much for as long as I've been turboed (and possibly even before that, as I never had an EGT gauge until I turboed). I've been seeing EGT's as high as 1600F when drivIng 80mph or so and up, or basically 4500 rpms and up. To me that seems a bit high, but for all I know it could be normal. I have AFR's about 13.5 in that area and I increased the timing from about 37 to about 41 in that area of the map to see if it changes. It might've gotten a little better, but not by much. I'm not worried so much about detonation since it's not in boost at that time, but I'm worried about burning/dropping valves, melting my turbo's turbine wheel, warping manifolds, etc.

Am I worrying for nothing?

FWIW, I cant really say for certain what it does under boost, say if I go WOT while cruising at that speed. My autometer EGT is pretty slow reacting, and I don't want to be doing 120mph staring at my EGT gauge waiting for it to move.
anarchyx34 is offline   Reply With Quote
Old 08-26-2010, 10:44 AM   #2
Tour de Franzia
iTrader: (6)
 
hustler's Avatar
 
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,114
Total Cats: 351
Default

Yeah, that's too high. Are you sure the gauge is reading correctly? EGT that high with a non-retard spark table I'd guess the gauge is wrong.
hustler is offline   Reply With Quote
Old 08-26-2010, 10:44 AM   #3
Elite Member
iTrader: (1)
 
Join Date: May 2009
Location: Jacksonville, FL
Posts: 4,682
Total Cats: 216
Default

That is too rich for cruising.
You should AT LEAST be stoich while cruising, but with good tweaking you should be able to run leaner than stoich in cruise.

Also, what kind of ignition advance are you running at cruise/decel
Full_Tilt_Boogie is offline   Reply With Quote
Old 08-26-2010, 10:46 AM   #4
Miotta FTW!
iTrader: (24)
 
Splitime's Avatar
 
Join Date: Jun 2006
Location: Chicagoland, IL
Posts: 4,295
Total Cats: 26
Default

I tune my car into the 15s for cruise.

Also, what is the location of the EGT sensor?
Splitime is online now   Reply With Quote
Old 08-26-2010, 11:27 AM   #5
Junior Member
Thread Starter
 
Join Date: Oct 2007
Location: Staten Island, NY
Posts: 159
Total Cats: 0
Default

Yeah i know 13.5 is too rich for cruising. I purposely made it that rich in an attempt to bring EGT's down. I have it at 14.7-15 in the lower rpms though.

The probe is mounted just before the turbine inlet.
anarchyx34 is offline   Reply With Quote
Old 08-26-2010, 11:28 AM   #6
Miotta FTW!
iTrader: (24)
 
Splitime's Avatar
 
Join Date: Jun 2006
Location: Chicagoland, IL
Posts: 4,295
Total Cats: 26
Default

EGTs can go up with fuel and up when lean. Its about finding the sweet spot between fuel and ignition.
Splitime is online now   Reply With Quote
Old 08-26-2010, 11:33 AM   #7
Tour de Franzia
iTrader: (6)
 
hustler's Avatar
 
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,114
Total Cats: 351
Default

Quote:
Originally Posted by anarchyx34 View Post
Yeah i know 13.5 is too rich for cruising. I purposely made it that rich in an attempt to bring EGT's down. I have it at 14.7-15 in the lower rpms though.

The probe is mounted just before the turbine inlet.
I've seen more fuel make higher EGT temps. That position is wrong, its supposed to be 1.5x the port diamer from the head. Lean it out and play with spark. I bet a leaner mixture and more spark angle will reduce EGT.

I should have hooked-up my EGT a long time ago but I can't bring myself to drill into my manifold.
hustler is offline   Reply With Quote
Old 08-26-2010, 11:48 AM   #8
Elite Member
iTrader: (1)
 
Join Date: May 2009
Location: Jacksonville, FL
Posts: 4,682
Total Cats: 216
Default

EGTs will go up from less fuel when there is detonation, which I dont think is the case.
My bet is that you dont have enough ignition advance in high vacuum combined with too much fuel.
Lean that **** out to 15.5:1 and advance ignition in that part of the map until it stops lugging
Full_Tilt_Boogie is offline   Reply With Quote
Old 08-26-2010, 12:11 PM   #9
Junior Member
Thread Starter
 
Join Date: Oct 2007
Location: Staten Island, NY
Posts: 159
Total Cats: 0
Default

How much ignition advance is too much? How high can I go? 45 degrees? 50?
anarchyx34 is offline   Reply With Quote
Old 08-26-2010, 01:16 PM   #10
Elite Member
iTrader: (1)
 
Join Date: May 2009
Location: Jacksonville, FL
Posts: 4,682
Total Cats: 216
Default

About as high as 45, dont give it more than it needs though, just bump it up a little at a time until it doesnt lug.
Ive seen people get it tuned right so that they can cruise at 16-17:1 AFR without lugging, and get epic mileage.
Full_Tilt_Boogie is offline   Reply With Quote
Old 08-26-2010, 01:24 PM   #11
Junior Member
Thread Starter
 
Join Date: Oct 2007
Location: Staten Island, NY
Posts: 159
Total Cats: 0
Default

I'll have to give it a shot. Thanks.
anarchyx34 is offline   Reply With Quote
Old 08-26-2010, 01:42 PM   #12
y8s
2 Props,3 Dildos,& 1 Cat
iTrader: (8)
 
y8s's Avatar
 
Join Date: Jun 2005
Location: Fake Virginia
Posts: 19,038
Total Cats: 407
Default

so what are your EGTs under sustained boost?

Last edited by y8s; 08-26-2010 at 02:44 PM.
y8s is offline   Reply With Quote
Old 08-26-2010, 02:18 PM   #13
Junior Member
Thread Starter
 
Join Date: Oct 2007
Location: Staten Island, NY
Posts: 159
Total Cats: 0
Default

In 2nd or 3rd gear pulls it maxes out around 1400 or so. On long 5th gear pulls it seems to stay around 1600, but like I said the gauge is a little slow. What's with the super sized text? Is where I put the probe that bad?
anarchyx34 is offline   Reply With Quote
Old 08-26-2010, 02:48 PM   #14
y8s
2 Props,3 Dildos,& 1 Cat
iTrader: (8)
 
y8s's Avatar
 
Join Date: Jun 2005
Location: Fake Virginia
Posts: 19,038
Total Cats: 407
Default

actually nevermind. mine's in the collector too. i was thinking of something else.

theres two things that primarily affect EGT: timing and air fuel ratio.

why:

retarding timing moves the ignition event later in the engine cycle. EGTs go up with retarding timing because the combustion event is still occurring as the exhaust valves are opening.

similarly, leaner AFRs tend to burn slower than stoich. as you go leaner, the burn is completing, again, after the exhaust valves are opening .. and more heat gest into the exhaust.

I suspect also that a relatively rich AFR may also be burning slowly or incompletely and carrying some heat out the exhaust valves.

The first thing I would do is correct your cruise fuel to something around 14.7 or 15.0 to 1 and re-check your cruise EGTs. I run 37-39 degrees of timing at 15:1 and my cruise EGT is closer to 1200. Advancing much beyond 45 degrees may not do much of anything.
y8s is offline   Reply With Quote
Old 08-26-2010, 02:50 PM   #15
Tour de Franzia
iTrader: (6)
 
hustler's Avatar
 
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,114
Total Cats: 351
Default

I don't know how bad it is but some of your reading is from heat in the manifold rather than the actual exhaust gas temp. This is because the metal part of the manifold is hottest at and around the turbo, coolest at the head.

Next time you drive at night and cruise, pull over and quickly check to see if the manifold is glowing. This will tell you if the cast iron is above 700* or not. My cast iron manifold glowed at cruise and REALLY glowed on the dyno. My SS manifold only glows in boost; I'm not sure if this is due to the manifold or due to EGT.
hustler is offline   Reply With Quote
Old 08-26-2010, 02:55 PM   #16
Elite Member
iTrader: (2)
 
Join Date: Jan 2007
Location: Los Angeles, CA
Posts: 8,782
Total Cats: 119
Default

-subscribing
Faeflora is offline   Reply With Quote
Old 08-26-2010, 05:12 PM   #17
Senior Member
iTrader: (1)
 
Join Date: May 2008
Location: south texas
Posts: 1,419
Total Cats: 9
Default

steady cruise @ 80 mph = 1350* 14.9-15.1afr
wot at the track 80-140mph = 1550* - 1600* 11.5-11.7afr 10psi

my egt probe is installed right where yours is at, not sure what my timing is at in those cells but i'm sure it's mid-upper 30's

do what everyone else has said, set afr, then timing, and you should be good.
spoolin2bars is offline   Reply With Quote
Old 08-26-2010, 05:55 PM   #18
Elite Member
iTrader: (12)
 
Join Date: May 2007
Location: Austin, TX
Posts: 1,923
Total Cats: 0
Default

You also might want to verify that your base timing is correct.
JayL is offline   Reply With Quote
Old 08-26-2010, 06:03 PM   #19
Junior Member
Thread Starter
 
Join Date: Oct 2007
Location: Staten Island, NY
Posts: 159
Total Cats: 0
Default

Base timing is correct, verified with a timing light. Could the fact that my manifold is ceramic coated is what's making the EGT's at the turbo inlet higher? Does the coating work that well?
anarchyx34 is offline   Reply With Quote
Old 08-26-2010, 06:34 PM   #20
Tour de Franzia
iTrader: (6)
 
hustler's Avatar
 
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,114
Total Cats: 351
Default

Quote:
Originally Posted by anarchyx34 View Post
Base timing is correct, verified with a timing light. Could the fact that my manifold is ceramic coated is what's making the EGT's at the turbo inlet higher? Does the coating work that well?
I've also wondered this considering my old ceramic manifold. It glowed all the damn time which didn't alarm me...until I let it idle for 10-minutes and it continued glowing.
hustler is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Project Gemini - Turbo Civic on the Cheap Full_Tilt_Boogie Build Threads 58 12-13-2017 10:04 PM
Back to Stock Part Out!! Turbo Parts, MS2 Enhanced 01-05, Suspension, and MOAR! StratoBlue1109 Miata parts for sale/trade 16 10-02-2015 10:39 AM
Time to start learning and play with tuning The Gleas MEGAsquirt 3 10-01-2015 10:30 AM
Got bad Crank Angle Sensor and Random Misfire codes, but runs fine. Greasyman General Miata Chat 2 09-28-2015 11:44 AM


Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 10:19 AM.