Car at tuner. Engine falls on its face at 6k RPM. Whats the problem?
04-27-2016, 02:28 PM
#1
Car at tuner. Engine falls on its face at 6k RPM. Whats the problem? So I have my car at an out of state shop to do a Fast 92 intake install and tune. They installed my MMS 220 heads and the cam that Tony specced for me a few months back. Car has always ran great. They emailed me stating the car is taking a nose dive at 6k RPM and provided a dynograph. They suspected either the springs (brand new PACS Tony installed on the heads before shipping to me) or the Yella Terra Rockers I reused.
I obviously don't want to randomly throw parts at the car to fix the problem so I wanted to get some other opinions. The car did not have this problem when they did all the initial work and ran great and the only thing that has changed is the intake/injector/ and plug install. Nothing internal. I haven't really beaten on the car in the meantime either. I just wanted to get some second/confirming opinions before I start throwing parts at an issue that seems out of the blue.
I obviously don't want to randomly throw parts at the car to fix the problem so I wanted to get some other opinions. The car did not have this problem when they did all the initial work and ran great and the only thing that has changed is the intake/injector/ and plug install. Nothing internal. I haven't really beaten on the car in the meantime either. I just wanted to get some second/confirming opinions before I start throwing parts at an issue that seems out of the blue.
04-27-2016, 02:35 PM
#2
Call Tony Mamo and see what he has to say. He'll be your best source of information on the problem and might want to talk to the tuner. Being MMS heads, it's not likely the springs but pushrod lengths and rockers could be an issue.
04-28-2016, 01:45 PM
#4
Glad I called Tony. He said the curve was fine until the plummet at 6k and suspected either a spark issue (highly possible since I asked for colder BR7 EF plugs to be installed) or something getting sucked closed at that RPM- also possible since the car is speed density tuned and I bought a baffled 4 inch rubber hose to connect the lid to the new 92mm TB.
My question is if it were the plugs, what would cause the sudden issue at 6k? It sucks that I may yet again not get these installed even though I eventually want to spray the car.
My question is if it were the plugs, what would cause the sudden issue at 6k? It sucks that I may yet again not get these installed even though I eventually want to spray the car.
04-28-2016, 02:30 PM
#5
Seems doubtful that spark would be the problem. You might try doing a test run with the air filter removed just to ensure that something isn't blocking air flow when you reach high rpm's. Are you running bigger fuel injectors? OEM might not be capable of supplying enough fuel for your setup.
04-28-2016, 02:38 PM
#6
Seems doubtful that spark would be the problem. You might try doing a test run with the air filter removed just to ensure that something isn't blocking air flow when you reach high rpm's. Are you running bigger fuel injectors? OEM might not be capable of supplying enough fuel for your setup.
04-28-2016, 03:10 PM
#7
That is something else I did change. I went from Bosch 36 lbers to 42lbers. Car is at about 450 rwhp on the stock pump. I've been looking into getting an aftermarket pump but wanted to make sure I would have enough leeway so I'm only doing it once. So instead of the Racetronix drop in kit, I've considered getting a larger pump with regulator, etc.
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04-28-2016, 04:22 PM
#10
I did not measure the pushrods but this is the same shop that installed/ dynoed this head setup a few months back without issue.
The things that changed were as follows:
Ported 92mm Fast intake installed (previous intake was LS6)
Bosch 42# injectors installed (previous were 36#)
Colder Br7EF plugs installed.
Also I still had the MAF assembly on the car but removed it since both the last tune and this tune are speed density, so I purchased a 4 inch baffled rubber intake hose from Spectre.
04-28-2016, 05:23 PM
#11
How rigid is that 4" rubber hose?
I think its collapsing some at that RPM and restricting airflow to the engine like we briefly discussed yesterday. If I'm right it would look exactly like what your seeing on the dyno.....make sure your CAI and the entire air tract leading to the engine cant be compromised by collapsing for whatever reason
Watching the engine during a WOT run would confirm or deny whether the 4" rubber hose is your problem.
Check the gaps on the plugs.....in fact replace them like I told you to because they are too cold for this application anyway. If the gap is too large the plugs may not be firing enough at the higher RPM.....plus they are colder than you need as I mentioned which will adversely effect part throttle performance for no good reason....a warmer plug offers multiple benefits here
Ditch the plugs....run a TR6 at .045 - .050 gap.....watch the 4" hose on the dyno and report back.
No sense spinning yours or anyone else's wheels till you eliminate what I would say are situations that are high on the list of creating your issues.
This is not a spring or parts problem.....the engine is running perfect till something causes a spark blow out or an airflow obstruction and you immediately lose 80+ ft/lbs of torque. You would have to literally hear it on the dyno the fall off is so dramatic and so fast.
Do what I recommended yesterday please and lets go from there....its the logical approach to diagnosing this problem
-Tony
I think its collapsing some at that RPM and restricting airflow to the engine like we briefly discussed yesterday. If I'm right it would look exactly like what your seeing on the dyno.....make sure your CAI and the entire air tract leading to the engine cant be compromised by collapsing for whatever reason
Watching the engine during a WOT run would confirm or deny whether the 4" rubber hose is your problem.
Check the gaps on the plugs.....in fact replace them like I told you to because they are too cold for this application anyway. If the gap is too large the plugs may not be firing enough at the higher RPM.....plus they are colder than you need as I mentioned which will adversely effect part throttle performance for no good reason....a warmer plug offers multiple benefits here
Ditch the plugs....run a TR6 at .045 - .050 gap.....watch the 4" hose on the dyno and report back.
No sense spinning yours or anyone else's wheels till you eliminate what I would say are situations that are high on the list of creating your issues.
This is not a spring or parts problem.....the engine is running perfect till something causes a spark blow out or an airflow obstruction and you immediately lose 80+ ft/lbs of torque. You would have to literally hear it on the dyno the fall off is so dramatic and so fast.
Do what I recommended yesterday please and lets go from there....its the logical approach to diagnosing this problem
-Tony
__________________
www.mamomotorsports.com
Tony@MamoMotorsports.com
Anything worth doing is worth doing well. Build it right the first time....its alot cheaper than building it twice!!
www.mamomotorsports.com
Tony@MamoMotorsports.com
Anything worth doing is worth doing well. Build it right the first time....its alot cheaper than building it twice!!
04-28-2016, 05:52 PM
#12
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Looks like it was tracking 460+ at 6500. Through a strange 60 at that.
04-28-2016, 08:34 PM
#13
How rigid is that 4" rubber hose?
I think its collapsing some at that RPM and restricting airflow to the engine like we briefly discussed yesterday. If I'm right it would look exactly like what your seeing on the dyno.....make sure your CAI and the entire air tract leading to the engine cant be compromised by collapsing for whatever reason
Watching the engine during a WOT run would confirm or deny whether the 4" rubber hose is your problem.
Check the gaps on the plugs.....in fact replace them like I told you to because they are too cold for this application anyway. If the gap is too large the plugs may not be firing enough at the higher RPM.....plus they are colder than you need as I mentioned which will adversely effect part throttle performance for no good reason....a warmer plug offers multiple benefits here
Ditch the plugs....run a TR6 at .045 - .050 gap.....watch the 4" hose on the dyno and report back.
No sense spinning yours or anyone else's wheels till you eliminate what I would say are situations that are high on the list of creating your issues.
This is not a spring or parts problem.....the engine is running perfect till something causes a spark blow out or an airflow obstruction and you immediately lose 80+ ft/lbs of torque. You would have to literally hear it on the dyno the fall off is so dramatic and so fast.
Do what I recommended yesterday please and lets go from there....its the logical approach to diagnosing this problem
-Tony
I think its collapsing some at that RPM and restricting airflow to the engine like we briefly discussed yesterday. If I'm right it would look exactly like what your seeing on the dyno.....make sure your CAI and the entire air tract leading to the engine cant be compromised by collapsing for whatever reason
Watching the engine during a WOT run would confirm or deny whether the 4" rubber hose is your problem.
Check the gaps on the plugs.....in fact replace them like I told you to because they are too cold for this application anyway. If the gap is too large the plugs may not be firing enough at the higher RPM.....plus they are colder than you need as I mentioned which will adversely effect part throttle performance for no good reason....a warmer plug offers multiple benefits here
Ditch the plugs....run a TR6 at .045 - .050 gap.....watch the 4" hose on the dyno and report back.
No sense spinning yours or anyone else's wheels till you eliminate what I would say are situations that are high on the list of creating your issues.
This is not a spring or parts problem.....the engine is running perfect till something causes a spark blow out or an airflow obstruction and you immediately lose 80+ ft/lbs of torque. You would have to literally hear it on the dyno the fall off is so dramatic and so fast.
Do what I recommended yesterday please and lets go from there....its the logical approach to diagnosing this problem
-Tony
Apparently they couldn't get the car back on the dyno today but did get the plugs changed. I'll know more tomorrow.
04-28-2016, 09:04 PM
#14
It says flex boot....What did u expect from china.
I have the same plugs running almost 12 to 1 on pump gas .035 gap and the car is not liking much over 6500 now. I guess I will go back a step there as you are. Good thread!
I have the same plugs running almost 12 to 1 on pump gas .035 gap and the car is not liking much over 6500 now. I guess I will go back a step there as you are. Good thread!
Last edited by handyandy496; 04-28-2016 at 09:18 PM.
04-28-2016, 10:45 PM
#15
Not very- at all.
Amazon.com: Spectre Performance 9770 4" 22.5° EPDM Flex Boot: Automotive
Apparently they couldn't get the car back on the dyno today but did get the plugs changed. I'll know more tomorrow.
Amazon.com: Spectre Performance 9770 4" 22.5° EPDM Flex Boot: Automotive
Apparently they couldn't get the car back on the dyno today but did get the plugs changed. I'll know more tomorrow.
Get a curved aluminum pipe or 4" curved plastic section and then just use a rubber coupler/hose clamps on the end of both sides.
Plugs and ditching that coupler should wake this baby up!! (dont forget I speculated you had something collapsing ahead of the TB before you told me about the cheesy coupler purshase.....LOL).
Looking forward to yuor feedback
-Tony
__________________
www.mamomotorsports.com
Tony@MamoMotorsports.com
Anything worth doing is worth doing well. Build it right the first time....its alot cheaper than building it twice!!
www.mamomotorsports.com
Tony@MamoMotorsports.com
Anything worth doing is worth doing well. Build it right the first time....its alot cheaper than building it twice!!
04-29-2016, 12:39 PM
#17
What size headers are you running? Take a look at my thread: https://ls1tech.com/forums/dynamomet...8-headers.html
I went from 1 3/4" headers to 1 7/8" headers, and it started falling on it's face after 6,000 RPM's. According to Brian Tooley, it's over-scavenging. He stated that the AI Dart/RHS heads have a really good exhaust port/flow, and coupled with a bigger exhaust valve, that's why I'm seeing my issue. Brian stated that he's done a bunch of testing using bigger headers on heads with really good exhaust flow (i.e. AFR, Dart) and the MMS heads are no different, as they have great exhaust flow numbers. Just another thing to possibly look at.
I went from 1 3/4" headers to 1 7/8" headers, and it started falling on it's face after 6,000 RPM's. According to Brian Tooley, it's over-scavenging. He stated that the AI Dart/RHS heads have a really good exhaust port/flow, and coupled with a bigger exhaust valve, that's why I'm seeing my issue. Brian stated that he's done a bunch of testing using bigger headers on heads with really good exhaust flow (i.e. AFR, Dart) and the MMS heads are no different, as they have great exhaust flow numbers. Just another thing to possibly look at.
