Inlet Mods

[profstoff]

I've just put my 500 Griff on the rollers at Austec and got 259 bhp @ 5175 rpm and 307 ft.lb at 4030. Max attained rpm was 5375. Three things strike me about this
1 max power about average for an unmodded car
2 Torque figure is good
3 Car ran out of breath at high revs (torque dropped off quite quickly after 4400 rpm)
This leads me to thinking that an inlet mod such as enlarged plenum, trumpets etc would give me a useful increase without going to the expense of wilder cams and without sacrificing any drivability.
I know ACT doing inlet mods but is there anyone else out there?
Any thoughts from anyone?

[IPAddis]

profstoff said:

I've just put my 500 Griff on the rollers at Austec and got 259 bhp @ 5175 rpm and 307 ft.lb at 4030. Max attained rpm was 5375. Three things strike me about this
1 max power about average for an unmodded car
2 Torque figure is good
3 Car ran out of breath at high revs (torque dropped off quite quickly after 4400 rpm)
This leads me to thinking that an inlet mod such as enlarged plenum, trumpets etc would give me a useful increase without going to the expense of wilder cams and without sacrificing any drivability.
I know ACT doing inlet mods but is there anyone else out there?
Any thoughts from anyone?

Max power is a tad low and at relatively low RPMs (I think mine makes max power at 5500). Torque is OK.

Have you had a cam change? I would check the cam, injectors and fuel pressure relief valve. If all those are OK, then I would consider induction mods.

A session with Mark Adams would work wonders.

Ian A.

[Steve_T]

I agree, if a car has good torque, but runs out of puff at the top end, it can be the cam that causes it. However, I found my car revved out much more keenly after Paul and Mark sorted out the top end fuelling - it was far too lean.

Steve.

[350Matt]

Another thing to consider is that these engines ( RV8's )do wear their cams out, most TVR grinds don't last beyond 55-60K as they are quite aggressive.

Time for a new cam perhaps?

Matt

[profstoff]

This is not what I was wanting to hear!
Both Rob Ingleby and Dave Batty reckoned the cam's okay when I bought the car and 260 bhp is about average for an unmodded Griff. It's done 65000 miles on the original cam and it's not unknown for cams to last 100 000 miles.
Nevertheless, I accept that one day I'll be swapping the cam out and that would be an excuse to put something more exciting in. What I'm thinking now is something that will give me a bit of a boost until that time but will still be usable then.
Thanks for the useful advice about the injectors and fuel pressure relief valve, I'll get those checked.
I think a session with Mark Adams is a given whatever mods I do.

[Jay Ayegees]

Forget about what way it behaves on a rolling road - what does it feel like on the road?
Has it ever left you feeling there's not enough power or torque?
Are you just feeling down because of the rolling road numbers and comparisons with other Griffiths?
An analogy :- A man with a 6" dick can experience a lot of satisfaction until in the loo he stands next to a man with a 10" dick - then he feels inferior.
I know it happened to me - what devastation even though I assured the other guy with the six incher that size didn't matter as long as he knew how to use it.

Edited by Jay Ayegees on Thursday 24th May 15:10

[profstoff]

Jay Ayegees said:

An analogy :- A man with a 6" dick can experience a lot of satisfaction until in the loo he stands next to a man with a 10" dick - then he feels inferior.
I know it happened to me - what devastation even though I assured the other guy with the six incher that size didn't matter as long as he knew how to use it.

I feel inferior standing next to the bloke with a 3" dick but let's not go there.

On the road the car is fine and was remarked as being one of the faster ones. It's not even that I'm disappointed with the RR results as Paul commented that the bhp is average for an unmodded Griff. My long term plan was to go down the normal route of cam and ecu upgrade. I'm just wondering if there is anything worthwhile I can do in the meanhwhile, especially as it seems to get short of breath at high revs.

[Pasco]

profstoff said:

Jay Ayegees said:

An analogy :- A man with a 6" dick can experience a lot of satisfaction until in the loo he stands next to a man with a 10" dick - then he feels inferior.
I know it happened to me - what devastation even though I assured the other guy with the six incher that size didn't matter as long as he knew how to use it.

I feel inferior standing next to the bloke with a 3" dick but let's not go there.

On the road the car is fine and was remarked as being one of the faster ones. It's not even that I'm disappointed with the RR results as Paul commented that the bhp is average for an unmodded Griff. My long term plan was to go down the normal route of cam and ecu upgrade. I'm just wondering if there is anything worthwhile I can do in the meanhwhile, especially as it seems to get short of breath at high revs.

Yep mate i would buy a 72mm plenum off fleabay along with a 45mm trumpet base.
Change the induction piping especially the 45deg elbow,afm to plen, and add a K&N filter.
Then pop it back on the rollers before i did anything else with the ecu,and i am sure you will be fine

[coetzeeh]

profstoff said:

This is not what I was wanting to hear!
Both Rob Ingleby and Dave Batty reckoned the cam's okay when I bought the car and 260 bhp is about average for an unmodded Griff. It's done 65000 miles on the original cam and it's not unknown for cams to last 100 000 miles.
Nevertheless, I accept that one day I'll be swapping the cam out and that would be an excuse to put something more exciting in. What I'm thinking now is something that will give me a bit of a boost until that time but will still be usable then.
Thanks for the useful advice about the injectors and fuel pressure relief valve, I'll get those checked.
I think a session with Mark Adams is a given whatever mods I do.

My cam was dead at 33k miles.

[clive f]

Hi Chris, YHM.

[profstoff]

clive f said:

Hi Chris, YHM.

Thanks Clive, YHM2

[steve-V8s]

Your really must think carefully about what you want from the car before commissioning a “tuner”. If you are happy with the way the car drives then it is well worth considering leaving as is. Reading all the information in your first post carefully I would suspect that if you proceed you will at least end up with a Cam, Injectors, Trumpets, re-map and a bigger number on the rollers. You may also end up with a rather smaller wallet and car that is fairly horrible to drive on a light throttle but not always one that is any quicker.

If you do go down the mods route then choose your tuner very very carefully.

If you were a cynic it may perhaps not be a surprise that before any tuning work cars tend to be a little low on the rollers and afterwards they are much improved. It seems quite rare for a car to be fine and dandy, no work required.

[Bluebottle]

Rebuild/new cam may not necessarily increase your terminal rpm's
I had my engine totally rebuilt last year along with a mc1 cam, the car pruduce a very impressive torque and power chart ( you can see them on my profile for the car) but my torque still peaks at 4200 rpm and engine will not rev over 5300rpm.
I am still running the factory ecu which i think is the problem as it may have the rev limiter set too low, as i have good fueling through out the rev range. The only other thing i can think of that would stop it reving freely above 5k would be unbalanced crank/components but my crank was reground during the rebuild which bring me back to the ecu holding it back.
Any thoughts from the guru's on here?

Edited by Bluebottle on Friday 25th May 10:11

[Gerjo]

Bluebottle said:

Rebuild/new cam may not necessarily increase your terminal rpm's
I had my engine totally rebuilt last year along with a mc1 cam, the car pruduce a very impressive torque and power chart ( you can see them on my profile for the car) but my torque still peaks at 4200 rpm and engine will not rev over 5300rpm.
I am still running the factory ecu which i think is the problem as it may have the rev limiter set too low, as i have good fueling through out the rev range. The only other thing i can think of that would stop it reving freely above 5k would be unbalanced crank/components but my crank was reground during the rebuild which bring me back to the ecu holding it back.
Any thoughts from the guru's on here?

Edited by Bluebottle on Friday 25th May 10:11

I'm certainly no guru but 5300 max rev doesn't sound right, should rev to about 6000, even on a standard mapping. Do you feel the limiter come in? Better talk to the shop that did the rebuild.

[Bluebottle]

Gerjo said:

Bluebottle said:

Rebuild/new cam may not necessarily increase your terminal rpm's
I had my engine totally rebuilt last year along with a mc1 cam, the car pruduce a very impressive torque and power chart ( you can see them on my profile for the car) but my torque still peaks at 4200 rpm and engine will not rev over 5300rpm.
I am still running the factory ecu which i think is the problem as it may have the rev limiter set too low, as i have good fueling through out the rev range. The only other thing i can think of that would stop it reving freely above 5k would be unbalanced crank/components but my crank was reground during the rebuild which bring me back to the ecu holding it back.
Any thoughts from the guru's on here?

Edited by Bluebottle on Friday 25th May 10:11

I'm certainly no guru but 5300 max rev doesn't sound right, should rev to about 6000, even on a standard mapping. Do you feel the limiter come in? Better talk to the shop that did the rebuild.

I read somewhere in the bible that some cars had a lower rev limiter, mine definately seems to lose a bank of sparks just over 5k. AS i said earlier the figure are exceptional for stock induction with 308bhp and 341 ft/lb peak figures, if I could find where that missing 500-1000 rpms is it would actually do the mythical factory figures i recon.

Edited by Bluebottle on Friday 25th May 11:08

[GreenV8S]

The lowest 'standard' rev limit I know of on RV8 TVRs is 5600 rpm, 6200 or so is more normal. But power tapering off at the top of the rev range doesn't sound like a rev limit to me, it sounds like a breathing/fuelling problem.

[GreenGriff400]

Jay Ayegees said:

Forget about what way it behaves on a rolling road - what does it feel like on the road?
An analogy :- A man with a 6" dick can experience a lot of satisfaction until in the loo he stands next to a man with a 10" dick - then he feels inferior.
I know it happened to me - what devastation even though I assured the other guy with the six incher that size didn't matter as long as he knew how to use it.

Edited by Jay Ayegees on Thursday 24th May 15:10

[John57]

My Griff made 267 bhp (221bhp ATW) at about 4800-5000 rpm + went to the limiter fine but quite flat. Torque dropped away just like yours though was a good figure.

I went down the inlet mods route albeit using expensive bits via Austec. The car was treated to an ACT triple plenum, associated trumpets, Bosch uprated AFM, uprated injectors and a Mark Adams remap.

The increase in power wasn't huge (about 18bhp at the wheels - ending up at 239 bhp) and on the face of it the car has less torque .... but .... it completely transformed the car into something that loved to go towards 6,000rpm rather than protesting at 4,500+. It was much smoother than as standard with less 'shunt' in traffic and was actually quieter (not always a plus point on a TVR I know ). It felt noticeably quicker than it had as standard and did it in a much nicer way.

The whole thing cost about £3,200 - so alot of money for 18bhp at the wheels - but the way the car changed is not reflected in the power figures but in the way it drove.

If I had of then chosen to put say a Stealth cam in as opposed to the standard one it was running I am sure the power would have gone up by the same again. I didn't want to go down he cam route as the car drove nicely and insurers seem to dislike uprated cams more than most other mods.

[rev-erend]

Chris - as per the last post (JOHN57)

You already have good figures .. and it's likely that you 'could' spend a lot to gain very little .. OK you may feel it's worth it but it's also possible to end up with a more un-reliable and un-standard car.

A re-map could gain you nothing.

Some careful diagnostics is probably more useful.

Sounds like a restriction causing the power tail off - althought there might not be much more to come..

Things like :

dropping fuel pressure (pump seen better days)

Injectors may have seen better days (22lbs injectors max out at 300bhp @ 43.5 psi) or there abouts...

Worth measuring the inlet manifold to see if they are ported to 45mm and that the velocity stacks are all still in place..

Dial guage to check valve lift is uniform ..

[Jay Ayegees]

Just drive the f'ing thing and stop looking for problems where none exist - if you want problems to worry about sell it and buy a Speed Six.