ITS car hits a flat spot between 7,000 and 7,800...what gives?
#1
Senior Member
Thread Starter
iTrader: (1)
Join Date: Oct 2006
Location: wisconsin
Posts: 519
Likes: 0
Received 0 Likes
on
0 Posts
ITS car hits a flat spot between 7,000 and 7,800...what gives?
Pretty much as the title. Last race my ITS car has developed a flat spot where it feels like it is draging the brakes (what it feels like, not what is happening). Then it clears out at about 7,800 rpm or so. Any thoughts.....
90 Rx-7 13B
90 Rx-7 13B
#2
Full Member
Join Date: Aug 2005
Location: Maumee, OHIO
Posts: 146
Likes: 0
Received 0 Likes
on
0 Posts
Let me take a shot try changing your plugs
or you 6th ports arnt opening?
#3
www.lms-efi.com
iTrader: (27)
Could be a variety of things. If you don't have any kind of fuel control you can expect mixtures in the 10:1 range in that area. That combined with a weak spark and you have misfire issues. Pretty common. Without data it's hard to diagnose. Plugs, wires, 20 year old coils/ignitors? You're past peak torque (peak fuel consumption) so it shouldn't be a fuel supply issue.
New problem or something that's always been there? Change anything before the weekend?
When you going to bring that thing down here and let me set it up for you?
New problem or something that's always been there? Change anything before the weekend?
When you going to bring that thing down here and let me set it up for you?
#4
Senior Member
Thread Starter
iTrader: (1)
Join Date: Oct 2006
Location: wisconsin
Posts: 519
Likes: 0
Received 0 Likes
on
0 Posts
Humm....
The plugs were new a few races ago....wires definitly could be...I will change out the ignitors too. No, this has just shown up the last race. It is a stock fuel system.
Oh beleive me...if I have the time and money you would be the first person I take it too. I know you would take care of it.... Once I get everything figured out and have some good showings on the car it will prolly be for sale. If I was going to get serious with it , I would definitly have you tinker with it. Once I am out of grad school I am planning on selling it to move into a formula series of some sort.
My freind had the same issue with a heavily street ported "track car." I still dont think he has it fixed either.
What plugs would you reccomend? I have stock 3rd gen in it now, that was what Mazda told me to use, what are your thoughts?
oh yeah, the only thing I changed was I wired the VDI open...I would think that would make it better, not create a problem.
Thanks guys!
The plugs were new a few races ago....wires definitly could be...I will change out the ignitors too. No, this has just shown up the last race. It is a stock fuel system.
Oh beleive me...if I have the time and money you would be the first person I take it too. I know you would take care of it.... Once I get everything figured out and have some good showings on the car it will prolly be for sale. If I was going to get serious with it , I would definitly have you tinker with it. Once I am out of grad school I am planning on selling it to move into a formula series of some sort.
My freind had the same issue with a heavily street ported "track car." I still dont think he has it fixed either.
What plugs would you reccomend? I have stock 3rd gen in it now, that was what Mazda told me to use, what are your thoughts?
oh yeah, the only thing I changed was I wired the VDI open...I would think that would make it better, not create a problem.
Thanks guys!
#5
www.lms-efi.com
iTrader: (27)
The stock plugs in the stock heat range work fine. I never could justify the expense of the fine wire plugs. I've also test the EGV plugs on the dyno and there was no difference in power at all. They're cheaper than the stockers so they're a good option IMO.
The VDI shouldn't make a difference unless you somehow wired it in the low rpm position. Then I could see it being soft up top but not just in one area.
Dunno...
The VDI shouldn't make a difference unless you somehow wired it in the low rpm position. Then I could see it being soft up top but not just in one area.
Dunno...
#6
Senior Member
Thread Starter
iTrader: (1)
Join Date: Oct 2006
Location: wisconsin
Posts: 519
Likes: 0
Received 0 Likes
on
0 Posts
hum, to cover my ***...teh VDI in the open position should be turned counter-clockwise, or against the lower ot the two stop tabs. (opposite of how it was at idle or engine off)
Trending Topics
#8
Moderator
iTrader: (3)
Join Date: Mar 2001
Location: https://www2.mazda.com/en/100th/
Posts: 30,802
Received 2,577 Likes
on
1,831 Posts
this is just fyi...
we ran the stock plugs, usually 9's all the way around, and had no trouble, they even last a decent amount of time.
my opinion is that the race plugs would be "better" mainly due to the colder heat range.
we ran the stock plugs, usually 9's all the way around, and had no trouble, they even last a decent amount of time.
my opinion is that the race plugs would be "better" mainly due to the colder heat range.
#9
Senior Member
Thread Starter
iTrader: (1)
Join Date: Oct 2006
Location: wisconsin
Posts: 519
Likes: 0
Received 0 Likes
on
0 Posts
Yeah, I have always ran the stock plugs as well, first time this ever came up.
racing beat suggests a BR10EIX I think...any thoughts on that.
As for the weak spark, my lame "test" is that I took all the plugs out and lined them up on the strut bar and put a cordless drill on a spare CAS - distributor, whatever, and they all seem to have the same healthy spark....is this a waste of time or am I actually ruling out weak spark as an issue.
Thanks guys!
racing beat suggests a BR10EIX I think...any thoughts on that.
As for the weak spark, my lame "test" is that I took all the plugs out and lined them up on the strut bar and put a cordless drill on a spare CAS - distributor, whatever, and they all seem to have the same healthy spark....is this a waste of time or am I actually ruling out weak spark as an issue.
Thanks guys!
#10
Senior Member
Thread Starter
iTrader: (1)
Join Date: Oct 2006
Location: wisconsin
Posts: 519
Likes: 0
Received 0 Likes
on
0 Posts
ok, so to add to my own question....the hack drill idea only spins the CAS to 3k rpm. I am trying to really cobble up a way to spin it a bit faster....more to come on my hillbilly diagnosis....maybe if I use some duct tape somewhere......
#12
www.lms-efi.com
iTrader: (27)
Testing spark the way you are doing it isn't telling you anything really. Since you aren't dealing with combustion pressures or turbulence there isn't much doubt you'll get a decent spark. And you only need to spin the CAS to 4000 rpm to show 8000 engine rpm. The CAS spins at half crank speed.
I've ran all 7s, all 9s, pretty much everything but the seriously expensive plugs and never had a spark issue. I'm guessing spending a bunch of money on the "race" plugs won't solve a thing.
I've ran all 7s, all 9s, pretty much everything but the seriously expensive plugs and never had a spark issue. I'm guessing spending a bunch of money on the "race" plugs won't solve a thing.
#13
Senior Member
Thread Starter
iTrader: (1)
Join Date: Oct 2006
Location: wisconsin
Posts: 519
Likes: 0
Received 0 Likes
on
0 Posts
humm...ok. Thanks for the advice as always..
Also, I meant I spun the CAS to 8,000 on the tach, i dont know the actual rpm of the CAS, just so I dont look like a tool.
Thanks!!!
Also, I meant I spun the CAS to 8,000 on the tach, i dont know the actual rpm of the CAS, just so I dont look like a tool.
Thanks!!!
#14
Moderator
iTrader: (3)
Join Date: Mar 2001
Location: https://www2.mazda.com/en/100th/
Posts: 30,802
Received 2,577 Likes
on
1,831 Posts
Testing spark the way you are doing it isn't telling you anything really. Since you aren't dealing with combustion pressures or turbulence there isn't much doubt you'll get a decent spark. And you only need to spin the CAS to 4000 rpm to show 8000 engine rpm. The CAS spins at half crank speed.
I've ran all 7s, all 9s, pretty much everything but the seriously expensive plugs and never had a spark issue. I'm guessing spending a bunch of money on the "race" plugs won't solve a thing.
I've ran all 7s, all 9s, pretty much everything but the seriously expensive plugs and never had a spark issue. I'm guessing spending a bunch of money on the "race" plugs won't solve a thing.
Thread
Thread Starter
Forum
Replies
Last Post
thecody59
1st Generation Specific (1979-1985)
14
01-23-16 11:52 AM
rx8volks
Canadian Forum
0
08-13-15 04:55 AM