Why did my car do this???????

[KW521]

Ok so tonight i was driving down the highway minding my own business and i got behind a 300zx. Looked pretty nice had exhaust for all i knew. Well 300zx took off and wanted a highway roll. I KNOW HIGHWAY RACING IS DUMB OK!!! But everyone gets stupid sometimes so i decided to be stupid and downshifted into 4th. I pulled on him sooo hard and passed him. I accidentally overrevved 4th(IDIOT ME!) i think cause my car like stuttered kinda cut went cut went so i shifted into 5th and was in high RPM's(wasnt too sure how high but my car did the same thing as 4th gear cut went cut went). So i let off and got back down to 65(my speedo only goes up to 110 and i peged that so i did not know how fast i was going. Soooo...... why the hell did my car do that. did i max our my speed that fast i dont think i could have cause it did it in 4th i didnt think it would be in 5th. Help me please i have no ideah what happend. Please tell me nothing is wrong with my car.

[KW521]

Oh ya stupid me i forgot to say i have an rb20det stock turbo and injectors. FMIC walbro fuel pump, 300zx fuel filter. SAFC2, boost gauge, full 3 inch from down pipe back exhaust.

[300Plus]

Just a guess but maybe you blew a intercooler coupler or worse... your turbo

[KW521]

no cause the thing is my car still ran fine and boosted and everything when i drove normaly.

[midnightsliding]

im kinda of tired but im not really seeing a problem sounds like u jsut hit your speed limiter.im not sure if RBs have them but KA and Srs do and that happenes to mine.

[z-monster]

hi guys,

i have a similar problem i experienced last night for the first time at an increased boost. i have been running my rb25det that is generally stock for the past yr and it has been boosting 0.4 bar standard. i increased the boost to 0.7 on monday last week and it has been great all till last night.

The story goes like this. I was chasing a ferrari f360 modena and we were cruising at 180 kmh untill he decided that he didnt want my old 1980 280zx on his tail so he drop a gear as i did and floored it.... i droped from 5th to 4th gear and floored it.... no problems till my rev shot up between 5000 to 6000 rpm. my engine felt like it was misfiring or backfiring. it was either short on fuel or the tuning isnt right somewhere. (i obviously dont knwo where i went wrong). my exhaust temp shot up to 850 degrees celsius. thats where i felt that there must be a problem with my fuel deliver system. i do however have a fuel pressure regulator which i have set to 38 psi and that has worked for the past yr running 0.4 bar boost.

it was as if my car had hit its rev limiter but that cannot be the case as my limit is at 7000rpm.

so the question is, why are our engines bogging at high rpm at 0.7 bar boost when it had no problems at 0.4 bar boost before? what else do i have to tune to get my car running reliably and safely without blowing anything?

oh ya... somtimes its ok to be racing on the highway!!!...

[KW521]

well my speedo only goes up to 110 mph and i had that pegged like nothing. so i dont know how fast i was going so i dont know if it was my speed limiter. I talked to a buddy of mine who knows cars well and is in mechanical engineering and another buddy of mine who knows cars pretty well. And they said that they would bet a lot of money that i maxed out my injectors....lol i do have an upgraded fuel pump and fuel filter but stock injectors...haha could that be it?

[armysweitzer]

i had a similar problem at high speeds (never did it at wot in 1-3) only 4-5. At first I had a broken spark plug. I replaced that and it was wonderful but now it seems to be doing it again. My car is running really rich and im wondering if im flooding the engine and it cant burn all the fuel off.

Just a guess IDK

[KW521]

That seems what could be happening with mine too cause i have an SAFC2 and my car runs a little rich so im guessing that i did max out my injectors....cause i have really good plugs in it NGK platinum they are like 12 bucks a piece

[Yellow4g63]

That seems what could be happening with mine too cause i have an SAFC2 and my car runs a little rich so im guessing that i did max out my injectors....cause i have really good plugs in it NGK platinum they are like 12 bucks a piece

Do you have it leaned out on the SAFC? you might have just hit fuel cut. Use to do it alot with my DSM when I had stock injectors and a SAFC but way bigger turbo. OR you hit the speed limiter, tho I did that once in my RB20 and it just cut the power on the car till the speed droped then it picked back up.

[skyHIGHblazing]

what up dud had the same problem -all i could guess was it was fuel cut off ori hit max speed - FREE WAY= NO CARS + 240sxi hit gov on stock motor i was happy - also i heard that u could cut the wire out - wait i read it some were i think it was rb20det.com yep thats it - so yah same thing happend to me - i got the same set up

if it turns out to be anything else **** let me know to

[z-monster]

hey kw521,

this is something i got from another site regardingthe same matter... i strongly feel its my fuel pump thats giving up so over this weekend i'm going to check out my spark plugs.. make sure that there isnt excessive carbon build up.... u should do the same.

[z-monster]

hey kw521,

this is something i got from another site regardingthe same matter... i strongly feel its my fuel pump thats giving up so over this weekend i'm going to check out my spark plugs.. make sure that there isnt excessive carbon build up.... u should do the same.

sorry i forgot to include the quote the last time

If your tune is "on". there are only two major causes of a high boost/high rpm misfire (and a lot of little ones). Fuel and spark.

Assuming your set-up is stock, your injectors are not running maxing out at .7 bar. Is the boost/vacuum line attached to the regulator? If so, you need to install a pressure gauge in the fuel line. Tape it to the windshield. Verify that the fuel pressure rises a proportionate amount to the boost. i.e. you are running 38psi, static, (vacuum line off), if the boost goes up to 10psi, fuel pressure should be 48psi. I would put my money here. That pump is probably not up to the task. You will see boost go up, and as the revs climb, fuel pressure will go down. Pumps lose a lot of capacity as the pressure is increased. Additionally, turbo engines have a higher BSFC than NA engines.

As pressuere in the CC increases, it takes more and more spark power to jump the gap. While the stock Nissan ignition is certainly up to the task, what of the plugs? I've seen lots of high-dollar (yen) "race" plugs give up the fight pretty quick when run on a daily driver. They may run fine until you lean on them. Electricity takes the easy road; this may mean the gap until the going get's tough in the CC. Then they may leak-to-ground through cracks in the insulation, not firing the charge. El-cheapo, non platnium/iridium plugs also have a hard time playing the boost game without some back-up in the form of a CDI, etc.

Be awaer that most in-cockpit EGT gauges are very slow resopnding. Open-junction sensors are the only ones you should believe. I've put HKS, Autometer, Defi, etc against my Omega hand-held. They are usually about 200 degrees behind on the climb. Once stabilized, they are the same, but in a gear where you pass through quickly, just be aware of what's going on if the gauge is climbing. A lean misfire will cause my Omega to show 1200 c, sometimes, where the aftermarket gauges will barely register a blip. The aftermarket stopped using open junction long ago because the sensors burn out pretty quick (reletive to an enclosed junction).

[KW521]

Wow z-monster thats a lotta good info thats nice. Well thats not what is wrong i talked to my mechanic who built my car and the master mechanic where i work.....Lol!!! SPEED LIMITER. For all of you RB20DET and RB25DET owners with stock ecu stuff your rev limiter only lets you go up 115 MPH or i think thats 180kmph im not too sure about metric stuff.....that sucks i thought i was hauling way faster than that but ya its your speed cut. My mechanic who has had a lot of rb20det engines says he has hit it speed limiter all the time! he says its no biggy but dont do it a ton prolly not good for the car. so Thats what happend to my car and z monster i think thats what happend with your car too.

[z-monster]

hey KW521,

what does KW521 mean anyway???? ok...hahah speed limiter.. what is that??? ok i forgot to tell yall... i have a speed limiter deflector!!!! hahahah my speed cut has been overwritten thats why i have been able to make 150mph runs!!! hhihihihih so for my case i need to nkow if i have enough fuel pressure.

what is the pressure of you fuel in stock form and in increased boost form??? i'm curretnly set at 38psi which by the way i hear is too low!!!!!

[Darius]

My speed limiter was overwritten by a pair of wire cutters. Just clip wire 53 on the RB25 ECU plug and you're good to go. I believe it's Y/G, but not sure.

[300Plus]

My speed limiter was overwritten by a pair of wire cutters. Just clip wire 53 on the RB25 ECU plug and you're good to go. I believe it's Y/G, but not sure.

Darius, looking at the rb25 ecu pin out it shows pin 53 as "Hicas Diagnostic wire/ speedometer" is that the one you cut and taped off ?

[annie4rb20]

Don't know much about RBs just yet, but this post has helped me out a lot.

http://racebread.com/smf/index.php?topic=636.0

[KW521]

LOL cut a wire thats all. Me personally i would go with a mines ECU for that. And i guess your right about fuel pressure. i dont know my fule pressure at all.....i know my injectors are stock a wimpy 270cc's

[wawazat8402]

LOL cut a wire thats all. Me personally i would go with a mines ECU for that.

Me personally would not. Mines ECU tunes are pretty aggressive especially for the downgrade in gasoline. Japan uses 100 octane, but on the MON system, which is about 95 octane on our RON system for measurement.

[DriftingisLame]

Z-monster, I highly doubt your problem is related to KW521's. 38 psi fuel pressure sounds really low, mine is set at 44... check to see what stock fuel pressure should be set at.

KW521- Welcome to speed limiter! You can max out your car's speed in 4th gear, so when you shift into 5th, your gonna get just a bunch more speed cut. Nothing to be worried about, just slow down or cut that wire