271 rwhp. And I am not happy. Help please

ricardoa1

Registered User
Now that I have some time to post this, I want to know what the experts think. In my quest for 300RWHP on stock internals I came up short. So I need help.
Alright I need alot of help.
At carlisle I had Brian Herron dyno tune my car. The base pull was something like 265rwhp. After that he adjusted air fuel to perfect. He noticed that the Knock sensor was kicking in at around 3000-3500rpms and ruining my numbers. So he dicided to turn of the sensor and monitor it himself with some added timing, and he found a lot of unexplainable detonation, but I managed 275rwhp. After that pull he turned the knock sensor back on and retarded the timing so i was at a safe level. Leaving me at 268rwhp. So i am not even at stock timing, he said once I get the problem fixed he can give me more timing and should see a big increase in HP.
Now comes the problem. I have a list of fuel delivery upgrades and a MP MPIC and cannot explain why this thing is detonating. I talked to Paul from BlueT and he suggested a couple of things, ill try them this weekend. But I would like to get other opinions too.
I am making about 15~ lbs, sometimes I peg it sometimes Im at 13 of Boost. Also I have a BBK AFPR and 42lbs injectors 255lps pump and a LMAF. My understanding is that this shoud be plenty of fuel.. Plus run colder plugs and a FMIC, to cool the air down. Brian even added that My Intake charge tems were way below average because of the FMIC.
So why is it that this thing is detonating like this.
I have not touched the internal engine Yet.
Any help is appreciated and sorry for the long post.
 
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do you know the motor has never been apart? if not maybe the heads have been milled, or maybe there is carbon build up on the heads.
 
maybe colder plugs like app103 colder thermostat vacuum leaks mine pinged when the hose wore out to the egr transducer or worn timing chain my dads 351m pinged a lot with old timing chain put in new chain and never pinged again thats all i can think of maybe old headgaskets ready to let loose could do this too
 
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Ricardo,

I don't think your doing very bad for bolt-ons. IMO, your not going to see much more power until you get more air flowing out of the engine. The stock heads and stock cam are most likely what's holding you back. Maybe a set of 1.8 rockers would help.

David
 
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Ricardo,
Nitrous will get you there!!
I had the same type of numbers with my were out Long Block and similar bolt-ons.
You have a sweet car, the next step may be heads and cam from Steigermeyer. That would put you in the the 310-330 range. Then a rod will shot out and you will have to do the bottom end. The list goes on and on. That is when the big bucks start.
Good to meet you at Carlisle

Gary
 
here's my thoughts.

The car made reasonable numbers. They weren't superb, but there were other cars there that day with heads and cams that were pulling similar numbers.

The problem is not fuel related either. It does fine with fuel, and gives exactly what I command it to. The flat 12:1 air/fuel is pretty good evidence that you don't have a fuel system or fuel pressure issue.

The problem has to be somthing like too much compression, carbon build up, or somthing engine related. Most super coupes will take 26-28 degrees of actual commanded spark advance at WOT. Since I had my NGS there, I can see what the EEC really is commanding. His would start pinging between 19-20 degrees. If I could have added that last 8 degrees, it would have been a nice power gain.

we also turned off the knock sensor to witness pinging. They pulled the plugs and it appears that it was detonating some even on the wimpy stock 95 timing curve.

ohh yea, it was detonating with after-blower intake temps of 86 degrees.

just my $.02.

Brian
 
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So get a water injection kit and run that for awhile. It might not add any power, but it will clean the cylinders.......
 
How is the exhaust system on this car? I imagine not stock, but what does it consist of? Cats? How old?

Never mind I see the exhaust in your sig...I kind of suspected an exhaust restriction.
 
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Thanks for all the replys. My exhaust upgrade is 96-97 Bird Tube Manifolds with the collectors opened to the max. Then custom downtubes and only keeping the third cat. Then custom 2.5 mid pipe split to two 2.25 pipes then to the flowmaster kit mufflers and out 2 or 2.25 (can't remember) tail pipes.
I think the exhaust has plenty of flow. Especially since i have not touched the heads to utilize anything bigger.

Anyways I just bought an electric fuel pressure gauge
and and aftermarket boost gauge so Ill now for sure that there is no fuel problems. But I dont think thats the problem. And so does Brian.

I bought the car with 42K miles back in 98 and seems like nothing was taken out before I owned it. The spanner nut was not abused and some of the bolts and nuts dont seem like have been removed. It now has 75k.
The other night I purged the Nitrous into the intake by mistake and the cranked the car. and a loud bang came out (ooopps) I though i fried the thing but I Uplugged the coil to vent any Nitrouus out the engine. Then plugged the the coil back on everything went back to normal. So I probably have bent rods that would lower compression, Not increase it.
Any more thoughs are welcomed.
 
93 Mark VIII said:
....Most super coupes will take 26-28 degrees of actual commanded spark advance at WOT. Since I had my NGS there, I can see what the EEC really is commanding....


Not to hijack this thread, but could you give me some info on this NGS?
 
So you do have a cat on there? The third one at that, I would suspect the thrid cat as the primary one for plugging. It is pretty far away from the engine, and the goofy design of integrating a catalyst into a T pipe....I might try getting that out of there.

If you removed the two upstream cats, they are the primary "burners" of pollution. Now you have MUCH more for this third cat is to take care of than it was designed for, plus as I mentioned it is really far from the engine, it might not be getting far enough up to temperature to really ignite. I would not be suprised at all if it is getting plugged.

The rest of your exhaust really doesn't sound that big either, the tubular manifolds are probably OK, but the single 2.5" midsection seems smallish.
 
Some opinions:

2.5" mid pipe is WAY WAY too small. Imagine giving the Hulk a coffee stirrer and telling him to take a deep breathe then exhale through it. A 3" or preferably 3.5" center pipe, dual 2.25" or even dual 2.5" pipes is the way to go. A single 2.5" pipe isn't big enough for the equivalent of a 400 CID naturally aspirated motor.

The stock heads won't get 300HP. The stock exhaust ports just suck. Even with all the bolt ons in the world, the stock exhaust ports will flow 110 CFM and that's it. Actually less than that since they only flow 110-115 CFM at .500" lift and the stock cam is only like .440" lift. With all the intake mods you've piled on I'm surprised the thing hasn't blown itself all over the highway yet. With all that coming in, it's prolly detonating because of unburnt gases not being able to get out. This will raise the combustion chamber temps so high it will detonate, it might be making the exhaust valve so hot it is causing the detonation. No way to fix it other than get more air moving. Cam and heads are definitely in order.

To be blunt, you've taken a bunch of parts and bolted them together. There's certain systems lacking (exhaust) and others that have been over-modified (intake) thus the result is less than the sum of the parts.

Get a good pair of heads and you'll be surprised. I'd kill to have your intake setup on my car. I think the stock (ESM modified) 94 intake plenum and stock intercooler are the bottlenecks on mine. It pretty much stops making more power around 4000rpm. If only I had another 2Gs to spend on a new plenum and IC setup.

Later,
Steve
 
That mid pipe does seem like a mistake. It's too small for both banks to be feeding into.

I was wondering if you could isolate the detonation to any particular cylinders. If it's on all cylinders, then I would agree more with issues related to head flow and exhaust restriction. But if it's isolated to some cylinders, it could be other things that would be more isolated.
 
Well to add. the exhaust gets extremely hot, I have been Around some SCs and. Mine gets the award for hot temps.
could this be a clogged cat?
I am out of funds and wont be able to touch the engine till next year. If not Longer, The engine runs very strong And head gaskets are holding on. So even if I blow the gaskets I wont have funds to get heads and cam. Which is pointless to do if I dont redo the bottom end at the same time.
So do most of you rule out the carbon build up or the heads machined?
I want to know how I can test to see if detonation is on all cylinders of just a few?
So what do you guys recommend If I intend to keep MY set up for a year or so. Underdrive the pulley going back to the stock 94-95 pulley or a 89 pulley that way I can add timing and atleast be at normal timing instead of retarded. This is what Paul recomended I do.
Again thanks for all your help.
 
What Steve said.

How much boost are you getting anyway? If it is over 15 its WAY too much.

I vote also for clogged cat. I say get the exhaust fixed first before you have headgasket issues. And I'd spend money on a mild head port before I'd go into the bottom end.
So even if I blow the gaskets I wont have funds to get heads and cam. Which is pointless to do if I dont redo the bottom end at the same time.
Sorry but this makes no sense. Your motor doesn't even have 100K on it yet. Mine has been making 300rwhp for 3 years now with 170+ on the clock. Ported heads were one of the best investments I ever made on the car.
 
Most of the time I peg the gauge but sometimes I see 13s.
All I was saying about the engine and heads is that. If I am going to spend the $2500 on doing the heads . I should just get the other $1500 and install rods and pistons. So I dont have to do it again after the heads and cam do any damage.

Ill cut out the third cat soon be the rest I have to hold off on, so I want to know what I can do to get the thing to normal timing.
 
Perhaps a bad EGR valve if you have one but just curious if a power balance test has been done to isolate any weaker cylinders. Maybe a slightly fouled injector. Not a totally clogged one but enough when taken to the max or close to the max all others are at 100% but one and that is all it takes. One injector at 95% or less when up there at near full pulse width will not flow with the rest of the bunch causing a spike in A/F ratios for that cylinder.
Maybe carbon build up. Just guessin' right now. Good luck with the HP quest. Sound off when you solved your dilemma.
 
I have Mac shorties In my basement waiting to be put on, But Money is tight to make the downtubes and so forth.
Im going to swap S/C pulleys this weekend.
The car feels very slow on the low end with the timing like this. I can barely break the tires loose, when before I had no problem laying a nice patch. Its good on the top end though.
Ill also see if I replace the EGR valve.
Now that I dont have a tuner, I have a chip, I have to wait till Brian to sends it back with any timing advice.

I dont know who does the engine tests around here, can someone guide me to a place that usually deals with it. The dealer? Myself? Or a specialty speed shop?
 
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