Very scary compression numbers on my turbo car - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


General Miata Chat A place to talk about anything Miata

Reply
 
 
 
LinkBack Thread Tools
Old 10-02-2011, 10:08 PM   #21
Elite Member
iTrader: (3)
 
Join Date: Mar 2008
Location: Granbury, TX
Posts: 6,009
Total Cats: 583
Default

Sounds like he's planning to replace the valves and seats anyway.

Just a thought, did you do the test on a warm engine? That can make a difference. On piston aircraft, leakdown tests are required once a year, and it is always done on a warm engine. Mind you, clearances are a lot looser when cold on air cooled engines, but still.
hornetball is offline   Reply With Quote
Old 10-02-2011, 11:03 PM   #22
Elite Member
iTrader: (5)
 
Join Date: Dec 2010
Location: Raleigh, NC
Posts: 1,970
Total Cats: 49
Default

Sad to see this Hustler, I hope you figure out whats going on. Might not be a bad idea to skip a few events next year and put that money towards a rebuild if it turns out things aren't so good on the inside. I just bought a compression tester so I can get this done next weekend before I make the dive for parts for TT next year.
Seefo is offline   Reply With Quote
Old 10-02-2011, 11:25 PM   #23
Tour de Franzia
Thread Starter
iTrader: (6)
 
hustler's Avatar
 
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,114
Total Cats: 351
Default

.009" lash on the exhaust valves. Time to pull the head.

Could I have been too rich with such a long burn time that EGT is too high going out the exhaust valves? Maybe it's time to install that EGT gauge but I don't know that I can bring myself to drill into the AF manifold.

Last edited by hustler; 10-03-2011 at 12:58 AM.
hustler is offline   Reply With Quote
Old 10-03-2011, 12:09 AM   #24
Elite Member
iTrader: (5)
 
Join Date: Dec 2010
Location: Raleigh, NC
Posts: 1,970
Total Cats: 49
Default

sorry I am new here, what year is your car Hustler? and what do you mean by lash? (are you saying clearance between exhaust valve and shim?)
Seefo is offline   Reply With Quote
Old 10-03-2011, 12:11 AM   #25
Tour de Franzia
Thread Starter
iTrader: (6)
 
hustler's Avatar
 
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,114
Total Cats: 351
Default

yes, 99 engine.
hustler is offline   Reply With Quote
Old 10-03-2011, 09:04 AM   #26
Elite Member
iTrader: (12)
 
GeneSplicer's Avatar
 
Join Date: Sep 2009
Location: Birmingham, AL
Posts: 2,006
Total Cats: 147
Default

Well that sucks donkey *****... and I was all about seeing you there at NOLA. Hopefully there's nothing cracked. When are you planning on opening her up?
GeneSplicer is offline   Reply With Quote
Old 10-03-2011, 10:35 AM   #27
Tour de Franzia
Thread Starter
iTrader: (6)
 
hustler's Avatar
 
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,114
Total Cats: 351
Default

Quote:
Originally Posted by GeneSplicer View Post
Well that sucks donkey *****... and I was all about seeing you there at NOLA. Hopefully there's nothing cracked. When are you planning on opening her up?
I plan to pull the head off the Monday after TXMC and have it to the machine shop the next day. Forza 4 will be out that day so I will probably have some sort of a sickness that keeps me from going to work anyway. At this point with two bad engines, out of rubber for the track and out of rubber for street tires, I can't get the van. However, I can drive my ******* track car 8-hours to NOLA and be a man about it.
hustler is offline   Reply With Quote
Old 10-03-2011, 11:48 AM   #28
y8s
2 Props,3 Dildos,& 1 Cat
iTrader: (8)
 
y8s's Avatar
 
Join Date: Jun 2005
Location: Fake Virginia
Posts: 19,038
Total Cats: 406
Default

I have a full set of standard size supertech valves with the reduced size stem. brand new in their little paper wrappers. $259 plus ship.

you know you want that ****.
y8s is offline   Reply With Quote
Old 10-03-2011, 12:05 PM   #29
Tour de Franzia
Thread Starter
iTrader: (6)
 
hustler's Avatar
 
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,114
Total Cats: 351
Default

Quote:
Originally Posted by y8s View Post
I have a full set of standard size supertech valves with the reduced size stem. brand new in their little paper wrappers. $259 plus ship.

you know you want that ****.
I do if they're SS or Inco. Let me get the head off first and confirm the problem.
hustler is offline   Reply With Quote
Old 10-03-2011, 12:18 PM   #30
Elite Member
 
Join Date: Jul 2005
Posts: 6,454
Total Cats: 80
Default

Quote:
Originally Posted by hustler View Post
.009" lash on the exhaust valves. Time to pull the head.
.009" isn't bad enough to cause massively accelerated wear.

It has always been my observation that in terms of long-term durability, exhaust valve seal is the miata's weak point.
I notice this even on *bone stock* miata engines, with <50k miles. It puzzles me, that the 2 Civic I had and sold with >100k miles had perfect valve seal. One of them had mediocre ring seal in one cylinder.

So I really do think exhaust valve material *must* be upgraded for any performance builds.


Quote:
Could I have been too rich with such a long burn time that EGT is too high going out the exhaust valves?
<10:1 can cause sooty exhaust which traps flakes between valves and seats, which would cause seats and valve faces to start burning. It may stand to reason btw that the ability to run leaner using WI helps exhaust valve longevity; WI reduces EGT too.

You always mentioned detuning timing by 4-5* down from MBT. Did you do this on the dyno and note how much % torque this costs? Or did you dyno tune to MBT, then after the session, retard it 4-5*?

In my dyno tuning experience, at around 10 psi, 1-2* down from MBT produces noticeable torque loss, and 4-5* produces *huge* torque loss, and lots more EGT.
JasonC SBB is offline   Reply With Quote
Old 10-03-2011, 12:21 PM   #31
Tour de Franzia
Thread Starter
iTrader: (6)
 
hustler's Avatar
 
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,114
Total Cats: 351
Default

Quote:
Originally Posted by JasonC SBB View Post
.009 isn't bad enough to cause massively accelerated wear.

<10:1 can cause sooty exhaust which traps flakes between valves and seats.
It looks like Westley Snipes in there, I'm going to suck a can of Sea Foam through the vacuum hoses and see if it changes anything.

If this car makes 245whp at 11psi on 60% leak, I'm going to be in for a real treat after a valve job.
hustler is offline   Reply With Quote
Old 10-03-2011, 12:23 PM   #32
Elite Member
 
Join Date: Jul 2005
Posts: 6,454
Total Cats: 80
Default

Quote:
Originally Posted by hustler View Post
yes, 99 engine.
If the 99 head doesn't have money sunk into porting, and it's indeed the cause of the bad leakdown, then it's probably time for a VVT head.
JasonC SBB is offline   Reply With Quote
Old 10-03-2011, 12:27 PM   #33
Tour de Franzia
Thread Starter
iTrader: (6)
 
hustler's Avatar
 
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,114
Total Cats: 351
Default

Quote:
Originally Posted by JasonC SBB View Post
You always mentioned detuning timing by 4-5* down from MBT. Did you do this on the dyno and note how much % torque this costs? Or did you dyno tune to MBT, then after the session, retard it 4-5*?

In my dyno tuning experience, at around 10 psi, 1-2* down from MBT produces noticeable torque loss, and 4-5* produces *huge* torque loss, and lots more EGT.
Reduced by 4* and did another pull. Yes, it lost a bit or torque, and of course I've never monitored EGT. However, I'm running this:

I don't see how at 184kpa i could possibly burn a valve. It defies the logic of everything I know.
hustler is offline   Reply With Quote
Old 10-03-2011, 12:28 PM   #34
Elite Member
 
Join Date: Jul 2005
Posts: 6,454
Total Cats: 80
Default

Quote:
Originally Posted by hustler View Post
If this car makes 245whp at 11psi on 60% leak, I'm going to be in for a real treat after a valve job.
Are you sure the seal wasn't good at the time of the dyno pull?
JasonC SBB is offline   Reply With Quote
Old 10-03-2011, 12:29 PM   #35
Tour de Franzia
Thread Starter
iTrader: (6)
 
hustler's Avatar
 
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,114
Total Cats: 351
Default

Quote:
Originally Posted by JasonC SBB View Post
If the 99 head doesn't have money sunk into porting, and it's indeed the cause of the bad leakdown, then it's probably time for a VVT head.
I do not have the knowledge, computer, time, nor dyno time to do this right now. I also make more than enough power.
hustler is offline   Reply With Quote
Old 10-03-2011, 12:31 PM   #36
Tour de Franzia
Thread Starter
iTrader: (6)
 
hustler's Avatar
 
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,114
Total Cats: 351
Default

Quote:
Originally Posted by JasonC SBB View Post
Are you sure the seal wasn't good at the time of the dyno pull?
The only thing I'm sure of is my masculinity and physical prowess.

I am not, however the car drives exactly the same as the last time I dynod it. It's kind of easy to tell, when it's over about 85*f, I won't spin the tires in 3rd leaving my apartment. This still remains true now that it's just a touch below 85* again and I made a cloud of tire-smoke in 3rd a few days ago.
hustler is offline   Reply With Quote
Old 10-03-2011, 12:33 PM   #37
y8s
2 Props,3 Dildos,& 1 Cat
iTrader: (8)
 
y8s's Avatar
 
Join Date: Jun 2005
Location: Fake Virginia
Posts: 19,038
Total Cats: 406
Default

Quote:
Originally Posted by hustler View Post
I do if they're SS or Inco. Let me get the head off first and confirm the problem.
Stainless w/ black nitride. MAIVN-1204 / MAEVN-1204 model number.

Also have Toga valve seals, also new. $49?

you buy both at those prices and I'll cover shipping.
y8s is offline   Reply With Quote
Old 10-03-2011, 12:42 PM   #38
Tour de Franzia
Thread Starter
iTrader: (6)
 
hustler's Avatar
 
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,114
Total Cats: 351
Default

Quote:
Originally Posted by y8s View Post
Stainless w/ black nitride. MAIVN-1204 / MAEVN-1204 model number.

Also have Toga valve seals, also new. $49?

you buy both at those prices and I'll cover shipping.
I will buy them pending disaster and agreement from my machinist.
hustler is offline   Reply With Quote
Old 10-03-2011, 01:44 PM   #39
Senior Member
iTrader: (1)
 
Join Date: May 2008
Location: south texas
Posts: 1,419
Total Cats: 9
Default

Just fyi, my car came with an egt gauge and under wot at the track it sits at 1,600 1650* f
For the last four and a half years. You think your egt's are higher than that? How hot do they need to be to burn a valve? Could they be bent? Still don't understand how your car could run so good with any of the proposed scenarios. You don't know anybody with a real compression tester? Snap-on or craftsman at least. Also as someone mentioned, was the engine fully warmed up? My buddy picked the strongest pistons when he built the engine. Unfortunately, that also meant that the alloy expanded more than the other option. So much so that you can hear piston slap when I turn on the car first time in the morning. I always let it warm up a little while before driving, and never boost until it's fully warmed up.
spoolin2bars is offline   Reply With Quote
Old 10-03-2011, 01:48 PM   #40
y8s
2 Props,3 Dildos,& 1 Cat
iTrader: (8)
 
y8s's Avatar
 
Join Date: Jun 2005
Location: Fake Virginia
Posts: 19,038
Total Cats: 406
Default

Quote:
Originally Posted by hustler View Post
I will buy them pending disaster and agreement from my machinist.
please fwd paypal and phone number of machinist.
y8s is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
elesjuan's mediocre 95 Miata adventure (google fiber edition) elesjuan Build Threads 8 02-16-2016 09:36 PM
Mystery Engine Trouble. Halp, mt.net! vehicular General Miata Chat 12 09-14-2015 04:17 PM
VE values too low? compuw22c MEGAsquirt 4 09-12-2015 08:42 PM
Compression test results Colipto General Miata Chat 3 09-11-2015 02:44 PM
New here, saying hi, here's what I'm workin with. SuperSneakySecretSquirrel Meet and Greet 5 09-06-2015 09:30 PM


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 07:08 PM.