I have been running 20 lbs of boost on e85. The car had been fine until the other day. I was getting into boost and when it hit 15 lbs it just cut out and kinda backfired and sputtered. At first I thought the up pipe blew off as it happened before. I checked hoses and all was well. The car still runs fine and builds boost up until I hit 15 lbs then it does the same thing. There are no error codes and Scanmaster numbers are fine. Could I have blown the stock turbo? Hopefully it's something simple.
Boost loss/backfire after 15 lbs?
- Thread starter DaveyX87
- Start date
I'm surprised more people have not chimed in with their experiences. Another thing to check is for a vaccume leak somewhere. Only time I ever had a back fire was when my head gasket let loose. It popped two times, and everything looked fine. I didn't know what had happened. Then it popped for the third time and it was catastrophic. That's my experience with back firing, doesn't mean it's what you're experiencing. Just putting it out there.
check the plugs, also see if the coils are in proper working order. i had this happen to me it would backfire and breakup so bad you would think the transmission was slipping, at mid boost it would be fine but by the time you went WOT it would fall on its face.
my bet is on the plugs
my bet is on the plugs
- Joined
- Feb 18, 2006
Backfiring is usually a indication that something is wrong with the cam sensor. Pull the cap off and check the wheel and the screw. Any kind of play will cause issues.
Turbo Tinkertoy
New Member
- Joined
- Sep 30, 2015
What is your A/F at 10-15 psi boost? is egr still on eng? cat ? fuel psi at 10-15 psi boost? is there knock? spark plugs...gap? how old? plug wires ohms? boot condition? any codes in comp? what is maf reading? check your breather tube boots for cracks, is oxy sensor oscilating fast or slow with flat lines hi or low? also check your vac hoses for wastegate and controller. maybe try a hand vac to check wastegate for leaks. good luck
josh young
Member
- Joined
- May 12, 2008
I had similar issue with boost cutting at 15#'s and it turned out to be the cam sensor cap. With it running unplug it and go for a drive and see if it acts differently.
- Joined
- May 26, 2001
When using e-85 in our turbo cars you need to realize there are many factors to consider and your symptoms are typical of what we have seen in many conversions.
The first thing to consider is the alcohol is MUCH harder to ignite than gasoline. This mean your ignition system must operate at optimum so you have enough spark especially at higher compression when the boost level in increased.
I have seen at least 1/2 dozen converted turbo cars exhibit the exact situation you have encountered including my e-85 500+ HP street car. After many "changes" of various parts including 3 different new coil pack/modules, it was finally cured with the installation of the TR6 ignition.
Like the 6 examples I mentioned above, all those were cured by the TR6. A few other street conversions that are set at a lower boost have no issue.
Another point of reference is my race car the used 116 octane for years and only had to change the program for e-85 to run the same or more HP with no other changes. Certainly the MSD distributor ignition has an awesome spark, so NO issue there!
One issue I did find in the race car and other e-85 conversions is contamination in the fuel, mainly small rubber particles, which the alcohol has etched from the rubber lines. My street car has a new fuel tank and ALL new lines to prevent this issue, and all the race car old braided SS fuel line were updated.
In your case with a stock turbo and intercooler, your inlet air temps are sky-high even at 15 psi which will give you detonation, and even worse you are on the edge of pre-ignition where you do NOT want to be.
- Joined
- May 26, 2001
A couple more comments that I hope will be helpful.
Since you must have e2-3 times more fuel at WOT, it is imperative that you visually check fuel pressure at WOT which can be easily done with hose and gauge to view while testing at WOT.
Another problematic area we have seen is the in-tank hose the connects to the pump will deteriorate due to e-85, so we use a submersible hose that will resist alcohol.
A regular hose will get soft and not hold enough pressure and eventually fail.
Since you must have e2-3 times more fuel at WOT, it is imperative that you visually check fuel pressure at WOT which can be easily done with hose and gauge to view while testing at WOT.
Another problematic area we have seen is the in-tank hose the connects to the pump will deteriorate due to e-85, so we use a submersible hose that will resist alcohol.
A regular hose will get soft and not hold enough pressure and eventually fail.
No disintegrations
Well-Known Member
- Joined
- Dec 27, 2015
I agree with nick, have you pulled the plugs? How long has it been on e 85? You can try new plugs with the gap squished Waaay down. Try .022 and see if that helps. Closing the gap will help if the ignition is borderline. Also turbo Buick plugs can be bad and not look bad for whatever reason.
- Joined
- Feb 18, 2006
Question: how would closing the plug gap help with a back fire? When spark goes out it causes miss fire.
I haven't had time to work on the car lately. I plan to go through it next week. I appreciate the all the feedback. I have only been on E85 for a couple months. I put in a new gas tank, fuel pump, and teflon line kit from Racetronix. I have stock replacement Delco plug wires and NGK UR5's (i think). The coil pack is new as well.
I have been so busy that I haven't had much time to look at the car. Assuming the oil, coolant, plugs, and everything else look ok, should I look into getting the TR6 ignition? Will I have to change chips if so? My other option is just to turn down the boost.
- Joined
- Nov 30, 2009
The TR6 works great and eliminates ignition & coil pack problems of the stock set-up , plus has added features , like 2-step and Rev limiter . The Rev limiter saved my motor when my transmission started slipping at WOT 2-3 shift . You will need different plug wires for the TR6 . Also try these plugs with the TR6 , NGK BR6FS aka NGK 4323 . These are the next step colder than UR5's and have a recessed tip + they are only $2.50 each at AutoZone . They work great in my car !
Samhttp://www.autozone.com/external-en...spark-plug/505335_0_0/?CJPID=3649950&cmpid=cj
Almost forgot , no chip change needed for the TR6 .
A couple of people mentioned fuel delivery - a few times over the years my car did this, almost like you turned the key off as the boost hit 12-15 psi, sometimes with a small backfire. Of course I chased all the electronic reasons first, sigh. Check the owners manual to see how often the fuel filter should be changed, and realize that with your big e85 pump you are circulating twice as much fuel as stock, all the time. Stock, GM said to replace the fuel filter every other oil change 
. Quite a difference from the old carbureted every 30-50,000 miles I was used to. Way back, I was putting 15-20,000 miles a year on my daily driver, and I got lazy about the fuel filter a few times and got caught. After you shake the fuel out of the filter, blowing through it should be about like blowing through a couple of feet of 5/8" heater hose but check a new one (after it has some gas in it to wet the element) to see for yourself.
. Quite a difference from the old carbureted every 30-50,000 miles I was used to. Way back, I was putting 15-20,000 miles a year on my daily driver, and I got lazy about the fuel filter a few times and got caught. After you shake the fuel out of the filter, blowing through it should be about like blowing through a couple of feet of 5/8" heater hose but check a new one (after it has some gas in it to wet the element) to see for yourself.
