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Something wrong? 2015 genesis coupe

4K views 40 replies 9 participants last post by  JGowen 
#1 ·
So I bought a new 2015 genesis coupe ultimate automatic last year. I took it to the track last year and the best 1/4 mile time I got stock was a 14.4. That was with around 7 different passes. Most were around 14.8. The car only had around 2500 miles on it at the time, so I chalked it up to breaking in still. Fast forward to June. I had bought an injen intake and an sfr tune. I went again to the track and the best time I ran was a 14.1 and this was around 8000 miles on the car.
Everything I've seen/read about this car is that it should run in the 13s stock.
My 60 ft on my best run was a 2.05 or something similar. So I don't think the launch/traction was an issue. I have a friend who has a 350z and we run just about dead even. So I just feel like something isn't right.
I know some people have said that spark plugs can be gapped bad from the factory, could that really cause a signification performance issue?
I always use 93 octane.
I make sure to have traction control off and I leave it in "sport"mode when racing.
I'm just trying to get all the irrelevant stuff out of the way.
Could maybe it be a lemon?
Could I just be crazy and that's how it's supposed to run?
Anyways thanks everyone!
 
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#2 ·
What is the altitude of the track you are running at?
 
#4 · (Edited)
Haha well that rules that out....
Go to this thread and compare... I do know that this car is not a drag strip monster at all.....
http://www.gencoupe.com/#/forumsite/20478/topics/31841?page=1
And I am pretty sure that slushbox tranny is gonna not be quite as quick as a M/T R-spec.... Plus the R-spec is lighter (stock for stock)... I think mid to high 13's should be quickest you can run on a stock GDI 3.8..... All I am saying is as you go through that thread, try and compare Apple's to Apple's I guess.....
 
#5 ·
That's where my basis was coming from. I read basically I should be around 13.8 stock. So I figure I was basically about a second slower in the 1/4. That's a pretty big difference. I guess I should just take the time and check the plugs. Idk if that could make that big off a difference though.
I have ordered some mods and they are on the way. Headers test pipes and port and polished intake manifold.
I guess I'm just hoping that either I find out what's wrong before I install these, or hope these fix the problem.
I would hate to do all that work installing everything to find out I have a lemon and I need to uninstall everything for warranty issues
 
#6 ·
From what I hear tightening up the drivetrain is the place to attack first..... To squeeze as much power to the ground as possible..... There is a recent thread about this... Not sure who it is but he drags all day and basically wrote us all a how to on how to get this thing running at the strip... Best of luck
 
#7 ·
You don't have a lemon, the car is running fine. Remember, cars are not absolutely identical upon production, there are variances in building them. Some engines may produce slightly higher, some may produce slightly lower.

There are TONS of possible reasons why you are getting the results you are. Your tires may be over-inflated and not gripping as much as they could. The track itself may not have been well prepped, for that matter. Some tracks prep better than others, that's why different tracks get reputations for being "faster" or "slower" than others, if you can't hook you're not going to get the quickest times.

Also, you said you're in Florida. In June, with a daily high temp of alot+° and crazy% rel. humidity? Sea level is great, but if it's hotter than Hell it's going to affect your output because it affects your IATs. If you're getting massive heat soak between runs in the staging lanes, your engine is just sucking hot air. No bueno.

Spark plugs being incorrectly gapped can definitely make a difference, and for something that literally costs you nothing more than effort, it's worth checking.

Also remember that a .6-.7 second difference at the 14s times is a LOT different than 6.-.7 second difference at say the 9s times. I've had that much variation at the 14s times without changing anything at all on the car. With already having mods on the way, your average times are likely to begin dropping more anyway, so don't worry too much about it.
 
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#9 ·
So the biggest thing that made me think about times was the first time I ran, there was a 2011 genesis coupe there. I ended up taking with him and he was running 13.7 or so on most runs, then we had a chance to run together and that's when I ended up with my 14.4 that night, and he ran a 14.2 after spinning through tires. He had full exhaust, intake and tune. I just figured that with a tune and intake that would've gotten me down into 13s.
When I went the second time and for the 14.2, most of my runs were right around that time. So I definitely shaved a bit of time. Both times I felt like the car hooked well. No wheel hop or spinning.
It's just a little discouraging that my friend has a 2003 350z with 140k miles and we run dead even.
I guess my plan of action will be to take out the driver's side plugs for now and check them, see where they are at. Definitely not going to do the passengers until the new manifold is here so I don't have to take it off twice.
 
#11 · (Edited)
Stupid question, but you DID have Traction Control off (both stages) and you were in Sport Mode, right? Those 2 alone would slow you down a lot.

The other things I can think of are
- Tires...the stock BF Goodrich tires are garbage.
- Also, you may be at sea level, but a hot day with high humidity will give you a density altitude that could be up a couple thousand feet. 2,000 feet of elevation will reduce your HP by about 25 ponies.
- Driving skill - just sayin'...
- lower octane gas - no, it doesn't create less hp, but your ECU will retard timing to prevent detonation if the octane is too low. Less timing advance = less hp.

Edit: I read your post too fast and skipped right over the 93 octane, and TC off with Sport Mode. That narrows it down a bit.

Edit #2 : Did you have stuff in the trunk? That extra weight will slow you down, too.
 
#12 ·
And as far as dealing with heat... Titan has an incredibly awesome thread on ways to keep the temps down at the intake..... I mean he has done a great job detailing how to do it... And other things as well... Haha he is my "go to" on here right now
 
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#18 ·
As I wrote in another thread ,the sparkplug for the nissan GTR twin turbo v6 will work and is a heat range colder by 1 . Gap them to .041''.
 
#15 ·
Sounds like you're looking at all the right things. Even 8000 miles is still a fairly new engine. Might need some more hard miles to open things up. I'm subbed to find out if spark plugs help. Will you please post the gap of your plugs here after you check?

Just drove around with a friend last night showing him the car. It was like 78 as apposed to the average 95 I've been driving in. The car just ripped and drove great even with the extra passenger all because of like 17F. It's a totally different animal.
 
#16 ·
I'm at work now, going to try to check the driver's side when I get home as long as it isn't dark outside.
Ordered the port and polished intake manifold so I'll check the other side then.
Unless I notice that these plugs are way off.
Then maybe I'll check both.
 
#20 ·
Okay so got home and took out the two front plugs on the driver's side....
Both were .40 and looked fine. So unless the others aren't good I guess that rules out plugs.
Also every once in a while the car has a little rough idle, almost like a misfire. I thought maybe the plugs. But who knows. Maybe the other four are bad.
Either way not going to test that out until the new manifold comes in. Should I maybe just take the car to Hyundai and tell them what I'm noticing? Or am I just being crazy?
 
#23 ·
To those who still have the stupid engine cover on ,pull them off .It keeps under hood temps up . The reason these plastic pretty cover will never be seen on true hi performance engines ,they cause the engine to heat soak .These are put in place by the OEM so that non mechanical minded , and internet engine masters can falsely impress their like minded girlfriend about their new secret high $$$$$ fast as snail crap car .
 
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#24 ·
TB coolant by pass & catch can is a must .Info all over this forum on how to get your gen to run without investing to much $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$.
 
#26 ·
I have had the cove off since the first time I took it to the track. I also did the TB bypass when I installed my intake and tune.
Haven't done a catch can, but I can't imagine that would gain me any power. I could see it maybe extending the life of the engine but that's about it.
I wonder honestly if I should switch back to the stock ECU and see what happens. I've heard of people calling the canned tunes paperweights, so who knows
 
#28 ·
Catch can won't gain you any power, it'll keep the MASSIVE amount of carbon deposits on our intake valves from draining power and potentially causing valve stem failure. A catch can on your PCV side is absolutely a must. Trust me, at 10k miles I pulled my top end apart and did a manual cleaning and you would not believe how much buildup there was.
 
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#35 · (Edited)
2 sided story here .It will only gain HP if you are running mineral oil ,it will keep the octane level from dropping due oil diluting the gasoline. If you are running a true synthetic of high quality , then there is no power gain as the ecu will not pick up the lower octane value (knock sensor) and pull timing . It will save your valves from having issues either way .
 
#29 ·
Haha I need to take my engine cover back off. I just had it on there cuz I have opened good vents and have been washing my car like 3 times a week for God knows what reason.... It just helped keep soapy carp water off the top of the motor while the engine was hot. Now I am doing all my detailing at home in the garage when the car is cold like a smart man.....So why do I still have that stupid thing on there lolz. Time to go take literally 10 seconds off my life and rip that thing off!

But really I can't tell you why you aren't running the 1/4 with the times you want, but is your buddy in the Z running a Manual transmission? Maybe he has a hidden NOS 75 shot in there he is keeping secret ;)
 
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#37 ·
Which is why I'm done with drag racing .The 11.87 @ 117 was nice ,but it is a PITA to get our platform to do these numbers . There are no road racing courses near me so I'm just happy to have decent car that will run when needed it at the touch of a button .I pondered putting a supercharger on it but came to my senses .
 
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#34 ·
Track prep has a lot to do with it also. I have pulleys, intake, CBE and BTR canned tune and pull consistent 13.6 1/4(I have a 15' R-Spec) and running stock tires. I have done this on Us 131 motorsports complex and Milan in Michigan. This weekend I raced at another place(non prepped) called UBLY (in Michigan) and the best I could get was a 14.1.
You also have more weight, this is why I don't think you have an issue. Shorttrack's suggestions will help also, I have done some of them. Practice, Practice, Practice. But this car will never be super fast.
 
#36 ·
Cheap billet aluminum (nice looking )catch cans be purchased of of ebay and amazon all day for about $26.00-$30.00 .
 
#38 ·
These "senses" which you speak of, preposterous!! Don't listen to them, they lead you down the wrong path, one of simplicity and boredom! Do not give in to practicality and responsibility, instead slide sideways into ridiculousness at ludicrous speed!
 
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#39 ·
Supercharger would be nice but I haven't seen any kits anywhere.
Either way, for now I'm just going to build up as NA to get as much out of it as I can. Just got test pipes in. Waiting on headers and port and polished manifold. Throttle body sometime later this year. But I'm going racing in a couple weeks again so gotta save up for that
 
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