Guess the 280ZX Turbo RWHP based only on Dyno video

[rturbo 930]

First I did a quick compression test and determined that #5 had ZERO compression which meant either the piston went bye bye or a valve must be stuck open. I determined that I bent a valve by removing the valve cover and observing that the #5 intake valve lash pad was missing and the #5 valve spring was compressed with no pressure from the corresponding rocker arm...valve was bent in the open position and could not return to closed position...I do know a little bit about engines

 

Were you trying as usual to be a prick with this question?

 

Cleve

He was just asking a question, there is no need to attack him.

[cgmeredithjr]

He was just asking a question, there is no need to attack him.

 

No, he was implying that I was just guessing that it had a bent valve. He admits that he is a prick, I find the banter quite fun.

 

Cleve

[hoov100]

No, he was implying that I was just guessing that it had a bent valve. He admits that he is a prick, I find the banter quite fun.

 

Cleve

 

 

Dude, he was just asking a question. You are the only person here interpreting or implying something.

[jc052685]

First I did a quick compression test and determined that #5 had ZERO compression which meant either the piston went bye bye or a valve must be stuck open. I determined that I bent a valve by removing the valve cover and observing that the #5 intake valve lash pad was missing and the #5 valve spring was compressed with no pressure from the corresponding rocker arm...valve was bent in the open position and could not return to closed position...I do know a little bit about engines

 

Were you trying as usual to be a prick with this question?

 

Cleve

 

 

Thought I was clear? I said I was curious.

 

Not many people bend valves in these motors that I know of.

 

 

 

No, he was implying that I was just guessing that it had a bent valve. He admits that he is a prick, I find the banter quite fun.

 

Cleve

 

Never said I was, said I come off as one.

Edited October 20, 2010 by jc052685

[Tony D]

Yes I did, the summation of the thread was "509 HP at 36psi".

Then something about a TH400...

 

"That's a lot of boost for the horsepower", probably 10 to 16psi higher than I would have expected.

 

What's your point?

[cgmeredithjr]

Thought I was clear? I said I was curious.

 

Not many people bend valves in these motors that I know of.

 

 

 

 

Never said I was, said I come off as one.

 

LOL, sorry, I just assumed from some of your previous "holier than thou" posts that you were implying something else. Anyone who has raced with these motors (road racing) knows that it is very easy to bend valves when there is an over rev situation (usually missed shift). The motor ramped up so fast at 36PSI that I was caught unaware and the rev limiter was unable to stop the zing.

 

I apologize,

 

Cleve

[cgmeredithjr]

Yes I did, the summation of the thread was "509 HP at 36psi".

Then something about a TH400...

 

"That's a lot of boost for the horsepower", probably 10 to 16psi higher than I would have expected.

 

What's your point?

 

Tony, the point is that I believe this motor is making more than the Dyno Dynamics is reading, how, I don't know, but what is that flat line on the graph...is it the TH400 slipping? Everyone at Forged thought this thing was making MUCH more than the reading based on what they were seeing and hearing (not scientific I know). I know what a 518AWHP car, 565RWHP car, and a 637RWHP car feel like, I have owned them all...this car hits harder and pulls harder than all of them. Automatics can be difficult to get a good reading, so they say. On the road, the car accelerates hard from 5500 to 7500 or so, yet on the Dyno Dynamics it flat lines starting at 6000RPM (this is right where it is starting to pull the hardest on the road). I was on my way over to the DynoJet for a comparison when I bent the valve or valves.

 

Any ideas? I think the readings would be much different with a manual behind this motor.

 

Cleve

[hoov100]

Don't be fooled, turbo cars have a tendency to make you think it's making more power then it actually is. I would bet that if the graph is that flat the trans would be slipping or the tires would be spinning.

[cgmeredithjr]

Don't be fooled, turbo cars have a tendency to make you think it's making more power then it actually is. I would bet that if the graph is that flat the trans would be slipping or the tires would be spinning.

 

Hoover, did you look at the dyno sheet I posted, it's a pretty darn flat line. Don't be fooled? All the big HP cars that I have owned have been turbocharged except for one built N/A C6 Z06...I understand your point, but I am not a newbie in this arena.

 

Cleve

[jc052685]

Two questions, how is it you think the motor made it past the rev limiter? What method of limiting are you using?

 

And I am sure that there are a few hundred on here that would tell you from their extensive road racing experience these motors don't tend to bend valves. Especially in a motor that is supposedly built for such stress.

Edited October 21, 2010 by jc052685

[cgmeredithjr]

Two questions, how is it you think the motor made it past the rev limiter? What method of limiting are you using?

 

And I am sure that there are a few hundred on here that would tell you from their extensive road racing experience these motors don't tend to bend valves. Especially in a motor that is supposedly built for such stress.

 

If a motor ramps up fast enough with no resistance (the tires lose traction)it can easily go into a mechanical over rev. When the tires broke loose out on the road, the motor accelerated from 6000RPM to 8000+RPM in a millisecond. The limiter is there to of course assist in preventing this scenario but it cannot always catch it in time...do you believe that a modern stability management system can save you from an imminent crash? Microtech is set up to cut fuel.

 

I'll know more when I pull the head and have it inspected, maybe it needs better springs and valve train set up, I did not build it remember.

 

Yes, they can and will bend valves if over revved, I did not say that they bend valves just for the hell of it.

 

Cleve

[Tony D]

JeffP's engine has a bit more poop than yours and even boiling the tires in first, second, or breaking them to a boil in third at 75mph the rev limiter catches it EVERY TIME.

 

The only way to mechanically over-rev an engine is to put it (manual) in a lower gear and physically DRIVE it past the rev limit. Like down a 6% grade, or forcing a 2nd gear downshift engagement and dumping the clutch while you're still at 80mph... THAT will cause overrev and valve float/bending if not total catastrophic engine failure.

 

If you 'over revved it' then something is wrong with your rev limiter, or you're using cheap electronics.

 

The speed of light is a bit faster than an L-Gata accelerating a couple thousand rpms...

 

As for the 'flat line' it's entirely possible you have stonewalled the turbo, or simply met the physical flow limitations through the turbine or some point in the intake tract. Jeff P is making about 200 HP more than you are, on a GT35R, and will not get a flat line if he runs 15psi and runs all the way to 8500+.

Bump the boost to 22 or something like that, and it makes incrementally more power, but flatlines at 7000 with the same sloped ramp that it did at 15 to 17 psi.

 

That, IMO is the turbo running out of flow capacity at that pressure.

 

But what do I know about turbocompressors...

Edited October 21, 2010 by Tony D

[cgmeredithjr]

JeffP's engine has a bit more poop than yours and even boiling the tires in first, second, or breaking them to a boil in third at 75mph the rev limiter catches it EVERY TIME.

 

The only way to mechanically over-rev an engine is to put it (manual) in a lower gear and physically DRIVE it past the rev limit. Like down a 6% grade, or forcing a 2nd gear downshift engagement and dumping the clutch while you're still at 80mph... THAT will cause overrev and valve float/bending if not total catastrophic engine failure.

 

If you 'over revved it' then something is wrong with your rev limiter, or you're using cheap electronics.

 

The speed of light is a bit faster than an L-Gata accelerating a couple thousand rpms...

 

As for the 'flat line' it's entirely possible you have stonewalled the turbo, or simply met the physical flow limitations through the turbine or some point in the intake tract. Jeff P is making about 200 HP more than you are, on a GT35R, and will not get a flat line if he runs 15psi and runs all the way to 8500+.

Bump the boost to 22 or something like that, and it makes incrementally more power, but flatlines at 7000 with the same sloped ramp that it did at 15 to 17 psi.

 

That, IMO is the turbo running out of flow capacity at that pressure.

 

But what do I know about turbocompressors...

 

Is Jeff P running an automatic? I don't think a PT76GTS with a .96 turbine housing flowing into a 4" downpipe and exhaust is stonewalled. On the intake side, open compressor inlet for testing, 3" plumbing from compressor discharge to intercooler inlet and then 3.5" plumbing from intercooler outlet to 90mm TB...maybe I have a banana in my tailpipe?

 

No matter what the boost, the dyno plot flatlines around the same RPM.

 

Cleve

[bradyzq]

Looking at the 2 dyno graphs, they're VERY different. On the 435whp run, you're making about 275 at 5252RPM. On the 509whp run, you make only 180ish at the same RPM. Why would that be lower on a higher boost run?

 

On the 435whp run, you reach 400wtq at 5500RPM, whereas on the 509whp run, you're only at about 230wtq. Either you pulled massive amounts of timing after the 435whp run, and the tune took a step backwards, or something was already broken or leaking boost by the time you ran the 509whp run. Because, worst case, those two RPM points where I compared torque outputs should be the same on both runs.

 

Do you know what caused the bumpiness at 6oooRPM and up? Was the boost controller oscillating a bit?

Edited October 21, 2010 by bradyzq

[cgmeredithjr]

Looking at the 2 dyno graphs, they're VERY different. On the 435whp run, you're making about 275 at 5252RPM. On the 509whp run, you make only 180ish at the same RPM. Why would that be lower on a higher boost run?

 

On the 435whp run, you reach 400wtq at 5500RPM, whereas on the 509whp run, you're only at about 230wtq. Either you pulled massive amounts of timing after the 435whp run, and the tune took a step backwards, or something was already broken or leaking boost by the time you ran the 509whp run. Because, worst case, those two RPM points where I compared torque outputs should be the same on both runs.

 

Do you know what caused the bumpiness at 6oooRPM and up? Was the boost controller oscillating a bit?

 

Good points, here is what I found so far, valve seat for lunch anyone?

[ModernS30]

To be honest. That what happens when you buy something claimed to be extremely high HP from somebody else, then not go through it before you beat on it. Not saying it wouldn't have happened if you did crack it open before dynoing and everything. Just maybe it could have been prevented.

[cgmeredithjr]

To be honest. That what happens when you buy something claimed to be extremely high HP from somebody else, then not go through it before you beat on it. Not saying it wouldn't have happened if you did crack it open before dynoing and everything. Just maybe it could have been prevented.

 

Pulled the head before all of these shenanigans to fix some leaks and everything "looked" normal...not sure if you can tell when a valve seat is going to let loose.

 

Cleve

[BRAAP]

There is no way to predict if a seat is going to fall out, unless the head is cracked between the seats which could relax the press fit on the seat, or the head is a pre '76 with OE soft intake seats, which have a tendency to just fall out.

 

Being as this head is post '79, best guess is;

 

1) Head is cracked between the seats and the added heat of 400-500 HP expanded the head material enough to release its grip on the seat.

2) That seat was replaced at some point in the past and the shop that did the seat R&R didn't' have enough interference between the seat pocket and seat, so with added heat of 400+ HP, the sat fell out.

3) Enough heat from mild-moderate detonation was absorbed by the head quickly enough that the casting grew enough to relax its squeeze on the seat, allowing it to fall out. (small sharp spikes in dyno plot are sometimes a sign of inaudible detonation. If the dyno operator set the "smoothing" scale with enough resolution to show such).

 

Or some combination of the above.

[jc052685]

Should post up some pics of the ports while its apart.

 

 

Told you I did not think it was a bent valve, though it may be now lol.

[cgmeredithjr]

There is no way to predict if a seat is going to fall out, unless the head is cracked between the seats which could relax the press fit on the seat, or the head is a pre '76 with OE soft intake seats, which have a tendency to just fall out.

 

Being as this head is post '79, best guess is;

 

1) Head is cracked between the seats and the added heat of 400-500 HP expanded the head material enough to release its grip on the seat.

2) That seat was replaced at some point in the past and the shop that did the seat R&R didn't' have enough interference between the seat pocket and seat, so with added heat of 400+ HP, the sat fell out.

3) Enough heat from mild-moderate detonation was absorbed by the head quickly enough that the casting grew enough to relax its squeeze on the seat, allowing it to fall out. (small sharp spikes in dyno plot are sometimes a sign of inaudible detonation. If the dyno operator set the "smoothing" scale with enough resolution to show such).

 

Or some combination of the above.

 

Maybe the valve bent and then when it returned to the seat it caused the seat to become dislodged due to uneven strike?

 

Cleve