Need help finding missing power.

[kurtstuart]

I'm having a problem with my car being about 150hp down from where it should be.

Here's a small description of the car when it last ran good August 2016, ran 10.75@141:
91 Eagle Talon, stick shift street car, makes about 6-700whp. 3200lbs,
8.5:1 2.0L JE pistons, Manley Turbo Tuff rods, stock crank, line honed with ARP main studs.
Stock port head with stock valves. Small back cut on the intake valves, cleaned up seat/casting overhangs in the ports and chambers.
Cams are .440lift and 226* @.040 hydrualic roller. Installed with an intake centerline of 108, and a LSA of 111.5
Beehive valve springs with 97lbs seat, and 250 over the nose.
Home made intake based on a stock intake, runners cut to 7" long and a 4" tube welded on for a plenum.
12x24x3.5 Garret FMIC
63.5mm inducer turbo.
Pump E85 fuel, 8 rochester/delphi 72pph injectors, and 2 walbro 255 external fuel pumps.
Factory ecu with a modified program using a moates ostrich and TunerPro RT. Using a Pmas HPX-F2 for airflow measurement.

In March 2016,
At 17psi, AFR of about .75lambda, and 19deg of timing it made 427whp @8500 on a dynojet 248h
at 40psi it made 640 with a flat curve from about 7000-8500 with .75lambda at 14* of timing.
Don't know torque or exact RPM as the pickup wasn't working.
I ended up tweaking the tune, adding boost and working it into 140mph traps in August 2016.
With a little less boost and a different stock intake it went 137-139 in October. I put a bunch of street miles on it after this. According to the maf, and the fuel used along with air/fuel ratios, the car was moving about 70lbs/min of air at 40psi.

In Febuary of 2017, I pulled the motor to freshen it up,here's what I found:
1. Crank was cracked #4 rod rournal fillet nearest flywheel.
2. Crank/timing pulley had came loose and had worked on the key and had about 2-3* of slop. Damper mounts to timing pulley.
3. Valve guides were pretty worn.

I re-assembled the engine with another used good condition crack free crank, new rings and bearings. At this time I replaced the home made intake with a new JMF Race intake, and a set of SMP 120pph injectors replaced the second set of the 72's. I also used a different head with stock ports/valves, and some slightly softer springs, 82lbs seat, and 210 nose. I also tightened up the LSA quite a bit, to about 104 (as my current setup has a lot less exhaust pressure than I thought it would). With the boost set back to about 17psi, the car felt really strong, especially in the upper RPMs.


Here's were things go to hell. Shortly after getting the car running on the new engine, I build a new engine harness and switch over to an AEM Infinity ECU. After the install, I work on tuning, and it get up to about 30psi. The airflow and fuel flow shows that I am now moving close to 62bs/min, but at only 30psi now. This is very much inline with what others with similar setups are experiencing.

As I'm turning up the boost and feeding it some timing, The car really isn't picking up like I expect it to. Although it doesn't feel terrible.
I take the car to the track with this tuneup in it, expecting to see some mid 130mph traps. I program in 2 more psi just for good measure, and the First pass the car runs 122mph. 32psi boost and about 14* of timing .75 lambda. I decide it want's more timing, and add in 3* more ( at this point I'm past what I have ever ran) Car runs 125mph. At this point I'm disgusted (track was really poorly managed that night too).

I get home and plug the numbers from my datalogs into virtual dyno. I know it's a guess at best, but it lines up pretty well a dj, and roads are flatter than flat around here.
So the last street pull I made before I loaded it up on the trailer to head to track, the car made 522whp, ~29psi, 14*, 61lbs/min, 4pm, 85* air temp
First pass at the track it made 488,11.50@122, 31psi,14*, 66lbs/min, 1am, and 70* air temp.
Second track pass it made 505,11.50@125, 31psi,17*, 66lbs/min, 1:30am , and 70* air temp.
2 days later I make a street pull and it makes 520, 33psi,17*,69lbs/min, 12am, and 70* air temp.

At this point I'm stumped. I don't feel comfortable adding any more timing as I'm as high as I've ever been. Due to a previous issue I think something is wrong with the head, guides worn, springs soft, ect.. So now I buy and bnib head casting, clean up the ports, and assemble it with better springs. 97 seat, 250 nose. Car runs exactly the same. 538@32psi.

At this point I add 3 more degrees of timing, car makes 560, 32psi, 20* 69lbs/min, 12am, and 70* ait.

Grasping for straws, I advance the exhaust cam 7* and the car looses 50whp, and 5lbs/min, same boost.

So at this point I'm scared of breaking it trying to add timing I knock the boost down to 15psi, and its way worse on power. I end up putting the headgasket out trying close to 30* at 17psi, and it only made 380. I have been checking plugs with no sign of detonation. Obviously something is wrong with it, and its not just low timing.

I have checked that the ecu is doing what it says it does timing wise. I can set the whole map to 10*, and take it 9500 watching with the light, and it stays very very steady, right at 10*. Same at 0, 5,and 15.

The only new things on the car are the intake and the ecu, I see both making good power, so I doubt they are the issue.

Now back in 2014 it did the same thing as it is doing now. I ended up blowing it up when ahead came off a valve. Upon dissection I had a cracked crank, severely worn guides, and the springs had lost about 10lbs on the seat.
After this,I put a stock engine together, reusing the springs that had gone soft, and the car was instantly back to making power. This was short lived, as after a couple track trips it has suddenly lost a ton of power. I assumed the head was going away, hence my new head on the current engine.

I ended up building the engine that is in the car now and installed it in 2015, and it was back to normal. It seems like the power loss has to be something in the shortblock, (crank cracked), or the head. But I would think my new head has eliminated the head as a possibility.

Has anyone seen such an issue like a cracked crank cause a big powerloss? The car has never shown any symptoms that it has an issue. It runs/drives great, just doesn't make any power. I did pull 2 rod caps, and a main cap, and they look fine, just like a very small amount of dirt has gone through them.

I have everything to build a new shortblock, I just can't decide weather to replace the shortblock on a big guess, or keep looking for something else.

[DaveMcLain]

That's a pretty big change to the lobe sep. I just wonder if the little engine doesn't like that for some reason and with it tighter it doesn't fill the cylinder as well with a quality mixture and the timing requirement becomes greater which makes it more prone to problems with detonation.

[kurtstuart]

That's a pretty big change to the lobe sep. I just wonder if the little engine doesn't like that for some reason and with it tighter it doesn't fill the cylinder as well with a quality mixture and the timing requirement becomes greater which makes it more prone to problems with detonation.

That's exactly what I thought. Which is why I tried advancing the exhaust 7*. That would have put both the exhaust and intake 4* advanced from straight up, and shouldn't hurt anything. Both the power, and airflow went down.

Last year I had a smaller turbo on for a while, and I had a brain-fart playing with the cams, and thought a cam degree was 1/2 crank degree, I ended up having things all out of whack, and the car would barely idle. but it still ran 135-137 like that. The turbo stuff just seems so insensitive to that, especially when your running inducer limited.

[naukkis79]

E85 is hard to ignite at very rich afr's. As you changed ecu what happened to coil load times?

Are you tried to use leaner AFR's? Usually .85 lamdba is fine with E85 and that AFR is much easier to ignite.

[kurtstuart]

I think I found it. Not positive, but it seems like it's firing all the plugs at each firing event. I ended up swaping back to the old stock ecu and harness, when I was setting the timing, I notice the timing light seemed to flash much slower than it did with the other system on it. This was a pretty steady 1200rpm idle both times.

Either way, the car seemed to idle much smoother, and runs smoother all around. Power seems to be back, first time I have ever pedaled it in 3rd gear, It changed lanes way more violently than it used to lol.

[user-23911]

So you've gone from a stock ECU with wasted spark and a MAF tune to and aftermarket (AEM) ECU with sequential ignition and a SD tune?
You know that the knock control on the AEM won't work properly with the factory knock sensor?

[kurtstuart]

Ahh, no. I'm running them both with a maf. Speed density is for the birds. They are both waste spark. Don't care about the knock sensor. If you need a knock sensor to tune a turbo car you have no business touching the keys.

[user-23911]

Oh no??????


No, you probably don't need it for E85 because it tends to suffer from pre ignition not knock, that's with too much timing and too lean.You'll know when the head gasket lets go.
Essential though for proper pump fuel.

[kurtstuart]

It's essential for nothing. They kinda worked when the car was stock, once it's making 150/hole they are about worthless. Kind of like a wideband, sure it's neat and it gives you an idea, but if trust it blindly your an idiot.

[user-23911]

It's essential for nothing. They kinda worked when the car was stock, once it's making 150/hole they are about worthless. Kind of like a wideband, sure it's neat and it gives you an idea, but if trust it blindly your an idiot.

No wonder it blew up.

[user-23911]

When you've got too much timing to start with, you don't add more.
You take it away and see if the power drops and by how much it drops by.
If it drops a lot you might want to add a bit.
If removing some doesn't make much difference, don't add more.
That's what kills head gaskets, bearings and cranks.....bad tuning.
Same as using a bigger hammer.


Same goes with the fuel, 0.75 lambda might be too much but your lambda gauge is probably reading wrong.
Stick with a calibrated factory NB sensor alongside the WB as a backup.
As well as that, your fuel pressure will be all wrong, it always is in the 4G63 world. Yet they're all in denial.
You'll find out when you measure the pressure and do some flow testing.......trying to push 1000HP worth of fuel through a small FPR.


You'd really want to get rid of the AEM too, fit a flashable factory ECU instead, far better.

[user-23911]

As far as changing the cam timing........by 7 deg?
7 deg at the cam gear?
That's 14 deg at the crank.

[kurtstuart]

No wonder it blew up.

lol Stock flashable ecu? Fuel pressure all wrong? Stock NB? Who the [DELETE THIS POST] are you? It's a 122cu in 4cyl that weighs 3200lbs, and has run 9's on a cast wheel 60mm turbo and a basically stock manual transmission. I have a pretty good idea of how to tune the thing. It make's 800+hp on a $26 paper felpro headgasket and cheap ARP headstuds - it doesn't have a detonation problem.

Anyway, grave digging, but ended up finding out that the AEM wasn't happy with the factory cam driven crank angle sensor. Swapped to a real 12 tooth crank angle sensor, and things got much better.

Ended up making close to 800bhp at 33psi on a SF901. 64mm turbo at this point.

[Baprace]

When you have a question on this site , it helps to listen , not all answers are going to be right , but some may help you solve an issue , remember you built this problem and all this site is trying to do is help you find a way to solve your issues. I think when you made some changes to the new engine you changed way too many parts at once with out finding what each change was worth, the cam timming stands out to me and the injector changes are certainly major issues and like you said "7* cam timming advance change on a new cam" with totaly different numbers makes no sense to me. JMHO