Engine stats: ZZ430 (ZZ4 shortblock, ZZ5 fastburn heads, hot cam kit) FI stats: S&P Ram Port injection, custom manifold (NOT TPI-style) with TPI electronics (730 ecm). I have a Moates burner and adapter. This does NOT live in an F or Y-body. It's in a P. This engine is rated at 430hp with a 750CFM carb. I had it set up as a ZZ5 385hp fastburn and with a 48mm tb and ran it on the dyno. 273 at the wheels. Set it up as a ZZ430 with the hot cam kit, and it did 276 at the wheels. Upgraded it to a 58mm tb and spent 2 years calibrating the 730 ecm to get it smoothed out. It drives great, but now it only did 250 to the wheels. You can imagine the overwhelming disappointment after that much work. I'll attach a scan of the dyno graph with a/f. Air: 58MM TB. Fuel: 25# LS1 injectors w/adjustable regulator, 14" vacuum from cam. FP is set at 43 PSI with the vacuum disconnected. Spark: Stock distributor/coil units, external coil, 8mm plug wires to AC MR43LTS plugs (yes, stainless-steel marine plugs) gapped to .045. Base timing is at 10 deg. Exhaust is true dual 2" with cast ram-horn style manifolds to twin cats and twin bullet mufflers. I've attached my BIN calibration and a Datamaster UNI log file. Where is the other 150hp?? Thanks, Dave

You have some losses in the transmission and accessories, there goes around 50 HP or so.

The other 100 HP is lost in the Exhaust setup you have. Rams-horn manifolds may have been good back in the day of 250 HP 283s, but they have NO place on a 430ish HP 350. They are choking the living daylights out of your ZZ430. You need headers with 1 3/4" primary tubes and dual 2 1/2" exhaust. I have put 1 3/4" primary tube headers on mild 305 TPI engines with good results. You are giving up 75-100 HP with your current exhaust setup. Measure the backpressure if at all possible. You should be somewhere under 2 psi @ WOT and the top of 2nd gear.

The only headers that will work in this transverse mid-engine configuration are the Sanderson CC90's.



I've already had them on my car before and removed them in favor of the manifolds due to collector cracking and heat. However, they weren't coated, and definitely should have been. They have 1 1/2" primaries and a 2 1/2" collector. I don't know if anyone's ever successfully done a full 2 1/2" exhaust on a V8 Fiero before, I'm sure it would be a challenge especially with 2 cats and 2 bullets to fit everything in there and bend it properly. I would prefer not to chase power on the exhaust side if it can be avoided, I really don't want a loud car.

The exhaust side of the combo is where you are losing your power. If you don't want to mess with the way it is now, live with the power it is making. You could de-tune the engine to operate with more torque in a lower rpm power band and make the car more fun to drive. Just trade the cam for a smaller cam.

Why will late model Corvette L98 exhaust manifolds not work? They are essentially the same as the headers you have shown, just much better. The LT4 made 340 NET FWHP using them with a Dual 2 1/2" exhaust system. In reality the LT4 was capable of around 370 FWHP from the show-room floor.

http://cgi.ebay.com/ebaymotors/1992-...QQcmdZViewItem

Curious, why is the Fuel Injector Flow rate set at 20.69 lb/hr when you have 25lb/hr injectors?

Never thought of those manifolds before, fast355. Here's a pic of the engine on its cradle with the CC90 headers:

You're right, that's wrong! The LS1 injectors are rated to flow 24.9lb/hr at 43psi up to 29.8 gal/hr at 58psi. Could this be the missing link? I can do either one.

The exhaust is corking it as stated by Fast355. You need dual 2.5" pipes, better headers, and CATS that will flow. That will gain 50+ HP by the sounds of the engine setup. You need roughly 2.2 cfm of exhaust flow per HP. Check the specs on the cats and muffers.

Dyno chart

I'm just a sucker for weird setups....

Have you done any data scans while doing these dyno runs? What is your AF Ratio, max spark advance and the amount of spark retard (if detonation is occurring in the scan)?

My immediate reaction is detonation is occurring and the ECM is pulling a ton of spark advance out. Because of the retarding, you aren't hearing the detonation.

A quick way to verify, is to reduce the max retard (while in WOT) to just 1*. Then if detonation is occuring, you'll hear it immediately. Then re-work your spark curve (with the retard limited to 1*) until you no longer hear any detonation. This is "old school" tuning when they didn't have any fancy scan tools ... but it still works today.

And, try and dial your AF ratio to around 12.8. You may find this is best done at a dyno, once you got the spark curve worked out.

I have a set of FastBurns. Half of your exhaust port is blocked with those headers.

FastBurns are D-ports. Large D-ports.

Your headers are small.

I would be surprised if you didn't have exhaust leaks above the tubes on each port.

jms

That is why I recomeended the Corvette exhaust manifolds. The 113 heads used the same D-shaped exhaust port.

Is that 430 hp gross hp?If it is,then you can ROUGHLY calculte it this way:
430x0.8x0.82(gross hp->SAE hp->autotrans rearwheel hp)

That would equate to approximately 290 RWHP. But the most crazyd ever gets is 250 HP, about 20% less than he should.

Crazyd, in your graph, your AF ratio is lean at rougly 13.5:1 at the start @ 2500 rpm. You slowly richen close to the correct AF ratio at 5,000 rpm and then go overly rich. Those two alone would cost you some HP - possibly the 40 HP you are missing per the above formula.

I also think some playing with the spark advance may yield some extra gains - but it is unclear as you don't show what the spark advance and knock retard is while performing the run.

Of course, without knowing more about your setup (both the bin & mechancial components), it is difficult to offer any further suggestions for improvements.

richness is probly killing alittle power after 5500rpms, but i wouldnt worry too much on the 13.5 in the lower rpms. dynojets tend to make the airfuel abit leaner than normal street wot since its not a load bearing dyno.

i think you could see another 20whp with better airfuel up top but still seems way underpowered for that setup. with decent exhaust i'd expect 320whp thru an auto. with crappy exhaust 280-300 wouldnt be far from norm

my L98 all stock with shorty headers/HSR made 254whp running very lean...so you have alot of work to do. I bet your timing and such could be off.

This isn't an auto, it's a 5-speed manual mid-engine transaxle. How is that formula adjusted for a manual transmission?

I checked in with Sanderson and they make a special version of the CC90 headers with a D-port mounting plate. I may look into getting a ceramic-coated set of those next time I've got $350 sitting around collecting dust.

I noticed how the a/f got really rich above 5500 too. You can see the torque/power go down at the same time so I know it's affecting it, but I also think there are bigger problems to skewer. I changed the injector constant to 24.90 from 20.69 in a reflashed chip, and there was a definite SOTP improvement. I assume that would have contributed to the excessive WOT richness and it may have cured it.

I do think the 430hp rating is gross, I know it's with open headers. But bear in mind too that the only continuous accessories I have are an alternator and a water pump.

Even in spite of being down quite a bit from its power potential, this car is still scary f*ing fast. It's geared so short and pulls so hard that my hands come flying off the steering wheel and shifter if I'm not hanging on tightly enough. But we all know it's never enough.

I didn't have a PC connected to it while I was making the runs, so I don't have that info. I did post a bin and mechanical component details, what else do you need to know about the setup? The recommended total timing advance looks like it's supposed to be 32 degrees BTDC @ 3000rpm for this engine with a carb.

The bin only has the values that it's SUPPOSE to have. That is when everything is "perfect". But when you have a problem, you need the amount of knock retard that is occurring and how much spark the ECM is actually pulling-off. That can only be obtained by a data scan while the engine is running in WOT from a scantool like Diacom.

A scantool may show that you are encounter a lot of knock retard and it's pulling out a ton of timing. That will greatly reduce your power. And this typically occurs at higher rpms and it may be the reason for the sudden "rich" condition as lower the spark advance tends to result in richening the mixture. (This is why guys must add a little more fuel if they keep increasing the timing...the mixture becomes leaner with more spark advance).

Regarding the "formula" to convert from Gross BHP to RWHP, you would use .90 instead of the .82 for the second paramater. In other words 430 x .82 x .90 = 317 RWPH. The first .82 converts from Gross BHP to Net HP. 430 x .82 is 352.6 (lets say 350 Net HP) The second parameter is for the drivetrain loss. 10% is the typical HP loss for a manual transmissions and 18-20% is typical HP loss for automatics. Multiplying by .90 (instead of .82) would account for the 10% drivetrain loss.

The only thing I am not certain about, is if the trans-axle used in your Fiero has more more than a 10% HP loss than the Front Engine/Rear Drive/Manual transmission setups as used in a 3rd Gen F-body. The transaxle may have a slighly higher HP loss (maybe 12-15%), but the transaxle should be more efficient than an auto setup.

So, if the transaxle has the same drivetrain efficiency as a normal manual tranny (10%), then you should be getting around 315 RWHP.

If the transaxle is 12-15%, then your should be getting between 300-310 RWHP. So you are definitely missing some HP from the 250 RWHP you obtained in those dyno graphs that you posted.

Thanks, I'll take a closer look at my Datamaster logs when I go WOT and see if there's any timing being pulled out from knocking. As for transaxle efficiency, I would expect it to be at least as efficient, if not more so, than a longitudinal manual transmission. With no driveshaft and the trans/diff in one unit, there's a lot less rotating mass and less frictional loss. I would be thrilled with a streetable 310-320whp, and I think that should be attainable with this engine without compromising its drivability.

A stock ZZ4 crate motor, installed in a fiero with Sanderson headers and 4 speed manual made 309 whp. Several of the SBC fieros with built engines performing significantly low on HP have all had the rams horns, so I would start with ditching them and going with a higher flow exhaust.

As I mentioned earlier, the exhaust is choking it. Once you get that fixed then move on to the spark timing. Any engine that has a decent cam and heads will lose more HP than a smaller head & cammed engine with a choked exhaust. You have a good setup there but the exhaust doesn't flow and causes too much back pressure. Tap a pressure gauge into the manifolds and you will see what the problem is.

Okay, so does anyone have recommendations on a high-flow, 2.5" I/O catalyst? Is Random Tech worth the money or is a Catco 2506R going to be just as good?

carsound by magnaflow (i do believe it is now.)

i have heard good things about carsound and its cheaper than random tech i think

Were did you get the intake manifold?

I'm more curious what the intake runner length is, the port matching between the intake and heads, and plenum volume size?

The Fastburns have a large intake port and a short runner intake could totally screw with a small displacement motor and mismatched cam.

Found this thread(flywheel vs.rearwheel hp): http://forums.corvetteforum.com/show....php?t=1912961

Update: my alternator failed in January so I shelved all this for some other projects this year, but I finished the other projects and fixed the alternator, and now I'm back to working on this problem. I ordered some Speedway cast headers over the summer but they didn't fit, so I am going back to the Sanderson CC90 headers in the new D-port version to fit my fast-burn heads - but ceramic coated this time, so they don't crack or cause engine compartment heat issues. I know this will make a huge difference and will see if the 2" true dual exhaust is enough for it.