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Discussion Starter #1
This isn't a major problem or at least I hope it's not.

In 5th gear on the interstate I mash it and everything is good up to about 4500rpm and then randomly the engine will start making a popping noise like a misfire not a detonation. I put a stronger new coil on it today and new spark plugs gapped to .32 like the 7M-GTE. the boost does spike about 3psi when I'm doing that due to load and such but that should not be too much of an issue considering the car is tuned at 12:1afr. I can play with the adjustments when I go out tonite if anyone thinks that's the problem. it's just real hard to diagnose that on a dynojet becasue the guy that does the tuning on my car has no way of putting a load on it. so the tuning is not totally exact, but much closer then me trying to do with without a wideband.

if anyone could give me some insite on this issue it would be appreciated
 

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you are pinging. in 5th you are under max load and the extra 3psi at that much advance is causing pinging. either pull the timing ~2deg, or put octane booster in it when you fill up the tank with 93 octane.
william
 

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william is right... you are pinging.... your puling too much timing on 5th gear... get some mix of race gas or octane booster w/ regular 93 fuel or retard the timing as william or get a ignition like MSD 6BTM or any boost retard so that you can still time your car as a regular NA but the ignition will retard itself as per boost pressure...
 

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Hi Eric. Please give us a list of your mods, including fuel system..injector size, using RRFPR? Fuel computer, compression ratio, engine condition, etc. Thanks.
-Aaron
 

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Discussion Starter #5
current mods consist of:

6M-GE (stock) 9.2:1 compression, stock rebuilt ct-26 and manifold, all stock 7M-GTE intercooler piping, 295cc injectors, RRFPR, Walbro 255lph fuel pump, S-AFC, engine burns a tiny bit of oil under boost but not horrible, spark plugs still look good. stock ignition set at 10 degrees (stock). engine is fully tuned on the dyno at 12:1afr for saftey reasons. I'd rather run a bit rich then melt stuff like pistons.


Rabid Chimp said:
Hi Eric. Please give us a list of your mods, including fuel system..injector size, using RRFPR? Fuel computer, compression ratio, engine condition, etc. Thanks.
-Aaron
 

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there it is right there, 10 deg base, 12:1 a/f ratio at 9psi, in 5th under load spiking to 12psi and over 4500rpm it is popping cause the timing is at full advance.i dont know how many deg. the timing advances per 1krpm or id state the deg that the timing is at when your pinging. running a bit rich is good to not melt parts, but if you ping too much you can break a compression ring or even a ringland. then the motor will have to come out. seriously, either retard the timing a little, run octane booster with 93 octane gas if your gonna run the car that hard, or get an igniton to retard the timing a little under boost. also, right after you hear the popping you might want to pull over and check a plug and make sure it isnt white from running lean. at that much airflow the injectors might not be able to keep up, even at ~100psi fuel pressure. that can cause pinging as well.
william
 

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I didn't see any mention of the grade of fuel you are running. Even @ 7psi, when I first ran my newly turbocharged Mk2 (with 8.8:1 compression ratio), my car pinged very badly. I switched from regular gas to super, and the pinging issue subsided. Follow WilliamB82s advice on fuel. What boost controller are you using?
-Aaron
 

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Discussion Starter #8
oh yea always running 93 octane


Rabid Chimp said:
I didn't see any mention of the grade of fuel you are running. Even @ 7psi, when I first ran my newly turbocharged Mk2 (with 8.8:1 compression ratio), my car pinged very badly. I switched from regular gas to super, and the pinging issue subsided. Follow WilliamB82s advice on fuel. What boost controller are you using?
-Aaron
 

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he always runs 93 octane. and he has the wastegate shimmed to 9psi. the reason it spikes is due to the stock o2 elbow and crappy downpipe. not to mention shimming the wastegate prolly isnt helping but it works. it is put together and tuned well, but he didnt tune it in 5th.the added load and the added boost are whats causing the problem. too bad there isnt a device that will only retard the timing in 5th starting ~4krpm
william
 

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Discussion Starter #10
the injectors can definatly keep up...there is no question of that.

williamb82 said:
there it is right there, 10 deg base, 12:1 a/f ratio at 9psi, in 5th under load spiking to 12psi and over 4500rpm it is popping cause the timing is at full advance.i dont know how many deg. the timing advances per 1krpm or id state the deg that the timing is at when your pinging. running a bit rich is good to not melt parts, but if you ping too much you can break a compression ring or even a ringland. then the motor will have to come out. seriously, either retard the timing a little, run octane booster with 93 octane gas if your gonna run the car that hard, or get an igniton to retard the timing a little under boost. also, right after you hear the popping you might want to pull over and check a plug and make sure it isnt white from running lean. at that much airflow the injectors might not be able to keep up, even at ~100psi fuel pressure. that can cause pinging as well.
william
 

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Discussion Starter #11
I've just got the wastegate shimmed

Rabid Chimp said:
I didn't see any mention of the grade of fuel you are running. Even @ 7psi, when I first ran my newly turbocharged Mk2 (with 8.8:1 compression ratio), my car pinged very badly. I switched from regular gas to super, and the pinging issue subsided. Follow WilliamB82s advice on fuel. What boost controller are you using?
-Aaron
 

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just because your friends 900cc/min injectors work at 100psi doesnt mean that 295's will. remember the orfice on the 295's is much smaller and that much pressure will affect the spray pattern and may be causing fuel puddleing. either way you are pinging and it isnt good.
william
 

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Discussion Starter #13
listen....the injectors are fine at that much pressure. you can say as you wish william but we have had this discussion and I've had someone that knows WAY more about this stuff then both of us combined. this is the same person that tunes my car and the same person that makes like 60k a year working at a performance shop that does some pretty insane stuff. I have known this guy since I was in high school and he is just insane about everything. yes it's my friend brian at race related that tunes on the dyno with a calculator. when it comes to this kinda stuff I definatly value his expertise. tho half the time I dont understand all the physics stuff that he throws at me as to why exactly things are as they are I definalty dont ever doubt him when he says anything about tuning or fabrication or crazy building his own ECU's. they also build 1000hp lightnings there which is real insane. never thought you could get that much reliable hp out of a stock bottom end especially not an american one.


williamb82 said:
just because your friends 900cc/min injectors work at 100psi doesnt mean that 295's will. remember the orfice on the 295's is much smaller and that much pressure will affect the spray pattern and may be causing fuel puddleing. either way you are pinging and it isnt good.
william
 

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ok, so 36psi fuel pressure base, plus 4psi per psi of boost, at 12psi boost in 5th, thats another 48psi of fuel pressure, plus the origonal 36psi thats 84psi. the injectors are designed to run at ~40psi fuel pressure so thats just over double the pressure. even though the injectors havent broken or started leaking, anyone will tell you raising the fuel presure isnt the best way to get more fuel to the engine. but anyway, set that aside.

have you asked brian about your "popping" problem? and if so what did he say? also, whats the highest fuel pressure that he said you can safely take the injectors too?

also, have they finished any of the lightnings yet? last i heard they were going for ~700rwhp but ive never heard of one completed. or heard of one running at sunshine or bradenton. ive got friends that go nearly everyweek, and a 1krwhp lightning would stick out.
 

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Discussion Starter #15
yes I've physically seen 2 completed ones that were sold. and I've also seen the dyno sheets. he said that low impedence injectors would hold (without exploding) about 115-120psi. they have ran the trucks at sunshine once or twice but I rode in the 890hp harly davidson truck...real real insane.....aside from the point.....the AF ratios on the dyno would show quite a bit of variance on the multiple pulls that we did if the spray pattern was screwy. the point is after we got it at 12:1 we did 3 more pulls back to back to make sure that the figures stayed pretty much the same and they did. I'm not discounting the fact that it could be getting leaner under the load of 5th gear. not at all. I'm just trying to figure it out. I havn't tested it with the new plugs and stuff yet. they were kinda old. they had about 25k miles on them. I did get on it a little bit saturday night but didn't push it very hard. I'll go out and do that tonite once it gets later. I know this can be done without messing with the timing.


williamb82 said:
ok, so 36psi fuel pressure base, plus 4psi per psi of boost, at 12psi boost in 5th, thats another 48psi of fuel pressure, plus the origonal 36psi thats 84psi. the injectors are designed to run at ~40psi fuel pressure so thats just over double the pressure. even though the injectors havent broken or started leaking, anyone will tell you raising the fuel presure isnt the best way to get more fuel to the engine. but anyway, set that aside.

have you asked brian about your "popping" problem? and if so what did he say? also, whats the highest fuel pressure that he said you can safely take the injectors too?

also, have they finished any of the lightnings yet? last i heard they were going for ~700rwhp but ive never heard of one completed. or heard of one running at sunshine or bradenton. ive got friends that go nearly everyweek, and a 1krwhp lightning would stick out.
 

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Get some 5 gallon jugs of Toulene from the paint store, and add a gallon when you fill up...pinging will be gone, and turn up the boost a little more!
 

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Discussion Starter #17
sweet...that sounds like a plan.


82Spearco said:
Get some 5 gallon jugs of Toulene from the paint store, and add a gallon when you fill up...pinging will be gone, and turn up the boost a little more!
 

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how much will 1 gal of that stuff raise the octane of 15 gallond of 93 octane?
william
 

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85TurboMKII,get a timing boost retard, I run 15 psi with only 210 cc injectors with 85 to 100 psi of fuel pressure and two additional injectors. WITHOUT timing retard on will ping at 10 psi, you can feel the power reduced alittle but its better than a blown engine, been running high fuel pressure since 86 and only had one original fuel hose leak alittle after 12 years. If you run racing fuel you can nearly turn retard unit off and my timing is at 12 degrees and run 2 heat ranges colder on plugs.But also run different cams.When I run lean it never makes any popping noise,just the standard pinging sound(lift right foot :roll: ).
 

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williamb82 said:
how much will 1 gal of that stuff raise the octane of 15 gallond of 93 octane?
william
Tolulene is 114 octane. I figured 1 gal. will raise 93 octane to 94.4. Only prob is tolulene is about $10 a gallon. You gotta pay to play.

HTH

Nick
 
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