Tech-> C4 bolt on RWHP info inside

[tntcorvette]

I found the 05/99 issue of Corvette Fever with the '85 "Code Red" project car and thought i'de post some RWHP & RWTQ numbers so those of you who are intrested in doing performance upgrades can see what will do what.

'85 L98 with the 4+3 transmission put out 197.8 rwhp @ 4100 rpms and 288 rwtq @ 3200 rpms.

The car also @ 4600 rpms put out 190.0 rwhp and 216.9 rwtq.

The following parts were added:

TPIS fuel regulator
TPIS ported plenum
TPIS 52mm throttle body
TPIS 1 3/4" long tube headers
TPIS long tube runners
Power Effects exhaust
Random Tech Cat. Converter
Performance Resources Chip.

After all this including a basic tune up (cap, rotor, coil, plug wires and plugs) the same car put out 228.9 RWHP @ 4300 rpms and 314.7 RWTQ @ 3400 rpms. At 4600 rpms power is at 222.5 rwhp and 254.1 rwtq.

I'de also like to point out how much the headers helped. With all the above, less the headers the car put out 224.7 rwhp @ 4500 rpms and 313.2 rwtq @ 3400 rpms. With the above mentioned headers the car put out 228.9 rwhp @ 4300 rpms and 314.7 rwtq @ 3400 rpms. Now what is intresting is that @ 2700 rpms rwtq w/o headers was 296.6 and w/headers it is 306.7 and at 4200 rpms rwtq is 277.2 w/o headers and 287.4 w/headers.

RWHP @ 5400 rpms w/o headers and the above mentioned mods is 173.2 and w/headers it is 176.6

RWHP @ 4200 rpms w/o headers and the above mentioned mods was 221.7 and w/headers 228.0

Hope this helps anyone considering some basic mod's on a L98 car.

 

[vader86]

and then you have 85s with the stock intake getting .15 in the 1/4 after adding longtubes

I would suspect they might have benefitted from a heated O2 sensor on that 85 because they drastically reduced the backpressure (and hence heat) in the exhaust system.

 

[tntcorvette]

Yeah, the L98 exhaust manifolds are less than 1.5" wide...pretty small IMHO.

I belivey they used a standard one wire o2 sensor. Funny thing is that the magazine said installing the headers was pretty involved. I've only installed my hookers and they are pretty easy to install.


*Edit* I also think the RWHP numbers would be better, especially up high above 4000 rpms with a large intake manifold (accel or tpis)...the stock lower base is a big restricion too.

 

[ProfessorBlaze]

big big bump.

I am researching L98 parts for my father trying to get c4 going. I am having trouble finding threads with good set-ups, other than this one. can anyone chime in with other info than this thread?

I have seen some info about hooker headers, info above.
interested with finding info about head swaps.. engine swaps from later model c4's (lt1, etc.)

 

[Schrade]

Airflow limitations on L98 are on the intake side - SPECIFICALLY, the intake manifold.

The intake design was based on flow characteristics of TPI LB9 - IROC Z motor. That's the opinion of Ray T Bohacz, who wrote the best short article on tuning L98 I know of uh huh. It's in Corvette Fever 11/2000, and I have it scanned somewhere if you want it. PM me...

My first had L98, and it's a good motor, IF ... properly tuned.

 

[ProfessorBlaze]

thanks. If you can find it, that would be awesome.